literature review introduction to

How to write a literature review introduction (+ examples)

The introduction to a literature review serves as your reader’s guide through your academic work and thought process. Explore the significance of literature review introductions in review papers, academic papers, essays, theses, and dissertations. We delve into the purpose and necessity of these introductions, explore the essential components of literature review introductions, and provide step-by-step guidance on how to craft your own, along with examples.

Why you need an introduction for a literature review

When you need an introduction for a literature review, what to include in a literature review introduction, examples of literature review introductions, steps to write your own literature review introduction.

A literature review is a comprehensive examination of the international academic literature concerning a particular topic. It involves summarizing published works, theories, and concepts while also highlighting gaps and offering critical reflections.

In academic writing , the introduction for a literature review is an indispensable component. Effective academic writing requires proper paragraph structuring to guide your reader through your argumentation. This includes providing an introduction to your literature review.

It is imperative to remember that you should never start sharing your findings abruptly. Even if there isn’t a dedicated introduction section .

Instead, you should always offer some form of introduction to orient the reader and clarify what they can expect.

There are three main scenarios in which you need an introduction for a literature review:

• Academic literature review papers: When your literature review constitutes the entirety of an academic review paper, a more substantial introduction is necessary. This introduction should resemble the standard introduction found in regular academic papers.
• Literature review section in an academic paper or essay: While this section tends to be brief, it’s important to precede the detailed literature review with a few introductory sentences. This helps orient the reader before delving into the literature itself.
• Literature review chapter or section in your thesis/dissertation: Every thesis and dissertation includes a literature review component, which also requires a concise introduction to set the stage for the subsequent review.

You may also like: How to write a fantastic thesis introduction (+15 examples)

It is crucial to customize the content and depth of your literature review introduction according to the specific format of your academic work.

In practical terms, this implies, for instance, that the introduction in an academic literature review paper, especially one derived from a systematic literature review , is quite comprehensive. Particularly compared to the rather brief one or two introductory sentences that are often found at the beginning of a literature review section in a standard academic paper. The introduction to the literature review chapter in a thesis or dissertation again adheres to different standards.

Here’s a structured breakdown based on length and the necessary information:

Academic literature review paper

The introduction of an academic literature review paper, which does not rely on empirical data, often necessitates a more extensive introduction than the brief literature review introductions typically found in empirical papers. It should encompass:

• The research problem: Clearly articulate the problem or question that your literature review aims to address.
• The research gap: Highlight the existing gaps, limitations, or unresolved aspects within the current body of literature related to the research problem.
• The research relevance: Explain why the chosen research problem and its subsequent investigation through a literature review are significant and relevant in your academic field.
• The literature review method: If applicable, describe the methodology employed in your literature review, especially if it is a systematic review or follows a specific research framework.
• The main findings or insights of the literature review: Summarize the key discoveries, insights, or trends that have emerged from your comprehensive review of the literature.
• The main argument of the literature review: Conclude the introduction by outlining the primary argument or statement that your literature review will substantiate, linking it to the research problem and relevance you’ve established.
• Preview of the literature review’s structure: Offer a glimpse into the organization of the literature review paper, acting as a guide for the reader. This overview outlines the subsequent sections of the paper and provides an understanding of what to anticipate.

By addressing these elements, your introduction will provide a clear and structured overview of what readers can expect in your literature review paper.

Regular literature review section in an academic article or essay

Most academic articles or essays incorporate regular literature review sections, often placed after the introduction. These sections serve to establish a scholarly basis for the research or discussion within the paper.

In a standard 8000-word journal article, the literature review section typically spans between 750 and 1250 words. The first few sentences or the first paragraph within this section often serve as an introduction. It should encompass:

• An introduction to the topic: When delving into the academic literature on a specific topic, it’s important to provide a smooth transition that aids the reader in comprehending why certain aspects will be discussed within your literature review.
• The core argument: While literature review sections primarily synthesize the work of other scholars, they should consistently connect to your central argument. This central argument serves as the crux of your message or the key takeaway you want your readers to retain. By positioning it at the outset of the literature review section and systematically substantiating it with evidence, you not only enhance reader comprehension but also elevate overall readability. This primary argument can typically be distilled into 1-2 succinct sentences.

In some cases, you might include:

• Methodology: Details about the methodology used, but only if your literature review employed a specialized method. If your approach involved a broader overview without a systematic methodology, you can omit this section, thereby conserving word count.

By addressing these elements, your introduction will effectively integrate your literature review into the broader context of your academic paper or essay. This will, in turn, assist your reader in seamlessly following your overarching line of argumentation.

Introduction to a literature review chapter in thesis or dissertation

The literature review typically constitutes a distinct chapter within a thesis or dissertation. Often, it is Chapter 2 of a thesis or dissertation.

Some students choose to incorporate a brief introductory section at the beginning of each chapter, including the literature review chapter. Alternatively, others opt to seamlessly integrate the introduction into the initial sentences of the literature review itself. Both approaches are acceptable, provided that you incorporate the following elements:

• Purpose of the literature review and its relevance to the thesis/dissertation research: Explain the broader objectives of the literature review within the context of your research and how it contributes to your thesis or dissertation. Essentially, you’re telling the reader why this literature review is important and how it fits into the larger scope of your academic work.
• Primary argument: Succinctly communicate what you aim to prove, explain, or explore through the review of existing literature. This statement helps guide the reader’s understanding of the review’s purpose and what to expect from it.
• Preview of the literature review’s content: Provide a brief overview of the topics or themes that your literature review will cover. It’s like a roadmap for the reader, outlining the main areas of focus within the review. This preview can help the reader anticipate the structure and organization of your literature review.
• Methodology: If your literature review involved a specific research method, such as a systematic review or meta-analysis, you should briefly describe that methodology. However, this is not always necessary, especially if your literature review is more of a narrative synthesis without a distinct research method.

By addressing these elements, your introduction will empower your literature review to play a pivotal role in your thesis or dissertation research. It will accomplish this by integrating your research into the broader academic literature and providing a solid theoretical foundation for your work.

Comprehending the art of crafting your own literature review introduction becomes significantly more accessible when you have concrete examples to examine. Here, you will find several examples that meet, or in most cases, adhere to the criteria described earlier.

Example 1: An effective introduction for an academic literature review paper

To begin, let’s delve into the introduction of an academic literature review paper. We will examine the paper “How does culture influence innovation? A systematic literature review”, which was published in 2018 in the journal Management Decision.

The entire introduction spans 611 words and is divided into five paragraphs. In this introduction, the authors accomplish the following:

• In the first paragraph, the authors introduce the broader topic of the literature review, which focuses on innovation and its significance in the context of economic competition. They underscore the importance of this topic, highlighting its relevance for both researchers and policymakers.
• In the second paragraph, the authors narrow down their focus to emphasize the specific role of culture in relation to innovation.
• In the third paragraph, the authors identify research gaps, noting that existing studies are often fragmented and disconnected. They then emphasize the value of conducting a systematic literature review to enhance our understanding of the topic.
• In the fourth paragraph, the authors introduce their specific objectives and explain how their insights can benefit other researchers and business practitioners.
• In the fifth and final paragraph, the authors provide an overview of the paper’s organization and structure.

In summary, this introduction stands as a solid example. While the authors deviate from previewing their key findings (which is a common practice at least in the social sciences), they do effectively cover all the other previously mentioned points.

Example 2: An effective introduction to a literature review section in an academic paper

The second example represents a typical academic paper, encompassing not only a literature review section but also empirical data, a case study, and other elements. We will closely examine the introduction to the literature review section in the paper “The environmentalism of the subalterns: a case study of environmental activism in Eastern Kurdistan/Rojhelat”, which was published in 2021 in the journal Local Environment.

The paper begins with a general introduction and then proceeds to the literature review, designated by the authors as their conceptual framework. Of particular interest is the first paragraph of this conceptual framework, comprising 142 words across five sentences:

“ A peripheral and marginalised nationality within a multinational though-Persian dominated Iranian society, the Kurdish people of Iranian Kurdistan (a region referred by the Kurds as Rojhelat/Eastern Kurdi-stan) have since the early twentieth century been subject to multifaceted and systematic discriminatory and exclusionary state policy in Iran. This condition has left a population of 12–15 million Kurds in Iran suffering from structural inequalities, disenfranchisement and deprivation. Mismanagement of Kurdistan’s natural resources and the degradation of its natural environmental are among examples of this disenfranchisement. As asserted by Julian Agyeman (2005), structural inequalities that sustain the domination of political and economic elites often simultaneously result in environmental degradation, injustice and discrimination against subaltern communities. This study argues that the environmental struggle in Eastern Kurdistan can be asserted as a (sub)element of the Kurdish liberation movement in Iran. Conceptually this research is inspired by and has been conducted through the lens of ‘subalternity’ ” ( Hassaniyan, 2021, p. 931 ).

In this first paragraph, the author is doing the following:

• The author contextualises the research
• The author links the research focus to the international literature on structural inequalities
• The author clearly presents the argument of the research
• The author clarifies how the research is inspired by and uses the concept of ‘subalternity’.

Thus, the author successfully introduces the literature review, from which point onward it dives into the main concept (‘subalternity’) of the research, and reviews the literature on socio-economic justice and environmental degradation.

While introductions to a literature review section aren’t always required to offer the same level of study context detail as demonstrated here, this introduction serves as a commendable model for orienting the reader within the literature review. It effectively underscores the literature review’s significance within the context of the study being conducted.

Examples 3-5: Effective introductions to literature review chapters

The introduction to a literature review chapter can vary in length, depending largely on the overall length of the literature review chapter itself. For example, a master’s thesis typically features a more concise literature review, thus necessitating a shorter introduction. In contrast, a Ph.D. thesis, with its more extensive literature review, often includes a more detailed introduction.

Numerous universities offer online repositories where you can access theses and dissertations from previous years, serving as valuable sources of reference. Many of these repositories, however, may require you to log in through your university account. Nevertheless, a few open-access repositories are accessible to anyone, such as the one by the University of Manchester . It’s important to note though that copyright restrictions apply to these resources, just as they would with published papers.

Master’s thesis literature review introduction

The first example is “Benchmarking Asymmetrical Heating Models of Spider Pulsar Companions” by P. Sun, a master’s thesis completed at the University of Manchester on January 9, 2024. The author, P. Sun, introduces the literature review chapter very briefly but effectively:

PhD thesis literature review chapter introduction

The second example is Deep Learning on Semi-Structured Data and its Applications to Video-Game AI, Woof, W. (Author). 31 Dec 2020, a PhD thesis completed at the University of Manchester . In Chapter 2, the author offers a comprehensive introduction to the topic in four paragraphs, with the final paragraph serving as an overview of the chapter’s structure:

PhD thesis literature review introduction

The last example is the doctoral thesis Metacognitive strategies and beliefs: Child correlates and early experiences Chan, K. Y. M. (Author). 31 Dec 2020 . The author clearly conducted a systematic literature review, commencing the review section with a discussion of the methodology and approach employed in locating and analyzing the selected records.

Having absorbed all of this information, let’s recap the essential steps and offer a succinct guide on how to proceed with creating your literature review introduction:

• Contextualize your review : Begin by clearly identifying the academic context in which your literature review resides and determining the necessary information to include.
• Outline your structure : Develop a structured outline for your literature review, highlighting the essential information you plan to incorporate in your introduction.
• Literature review process : Conduct a rigorous literature review, reviewing and analyzing relevant sources.
• Summarize and abstract : After completing the review, synthesize the findings and abstract key insights, trends, and knowledge gaps from the literature.
• Craft the introduction : Write your literature review introduction with meticulous attention to the seamless integration of your review into the larger context of your work. Ensure that your introduction effectively elucidates your rationale for the chosen review topics and the underlying reasons guiding your selection.

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

• UConn Library
• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
• << Previous: Getting Started
• Next: How to Pick a Topic >>
• Last Updated: Sep 21, 2022 2:16 PM
• URL: https://guides.lib.uconn.edu/literaturereview

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• What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

• Quick Run-through
• Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and scholarly context
• Develop a theoretical framework and methodology for your research
• Position yourself in relation to other researchers and theorists
• Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

• Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
• Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
• Critically evaluate: mention the strengths and weaknesses of your sources.
• Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarise yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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How To Write An A-Grade Literature Review

3 straightforward steps (with examples) + free template.

By: Derek Jansen (MBA) | Expert Reviewed By: Dr. Eunice Rautenbach | October 2019

Quality research is about building onto the existing work of others , “standing on the shoulders of giants”, as Newton put it. The literature review chapter of your dissertation, thesis or research project is where you synthesise this prior work and lay the theoretical foundation for your own research.

Long story short, this chapter is a pretty big deal, which is why you want to make sure you get it right . In this post, I’ll show you exactly how to write a literature review in three straightforward steps, so you can conquer this vital chapter (the smart way).

Overview: The Literature Review Process

• Understanding the “ why “
• Finding the relevant literature
• Cataloguing and synthesising the information
• Outlining & writing up your literature review
• Example of a literature review

But first, the “why”…

Before we unpack how to write the literature review chapter, we’ve got to look at the why . To put it bluntly, if you don’t understand the function and purpose of the literature review process, there’s no way you can pull it off well. So, what exactly is the purpose of the literature review?

Well, there are (at least) four core functions:

• For you to gain an understanding (and demonstrate this understanding) of where the research is at currently, what the key arguments and disagreements are.
• For you to identify the gap(s) in the literature and then use this as justification for your own research topic.
• To help you build a conceptual framework for empirical testing (if applicable to your research topic).
• To inform your methodological choices and help you source tried and tested questionnaires (for interviews ) and measurement instruments (for surveys ).

Most students understand the first point but don’t give any thought to the rest. To get the most from the literature review process, you must keep all four points front of mind as you review the literature (more on this shortly), or you’ll land up with a wonky foundation.

Okay – with the why out the way, let’s move on to the how . As mentioned above, writing your literature review is a process, which I’ll break down into three steps:

• Finding the most suitable literature
• Understanding , distilling and organising the literature
• Planning and writing up your literature review chapter

Importantly, you must complete steps one and two before you start writing up your chapter. I know it’s very tempting, but don’t try to kill two birds with one stone and write as you read. You’ll invariably end up wasting huge amounts of time re-writing and re-shaping, or you’ll just land up with a disjointed, hard-to-digest mess . Instead, you need to read first and distil the information, then plan and execute the writing.

Step 1: Find the relevant literature

Naturally, the first step in the literature review journey is to hunt down the existing research that’s relevant to your topic. While you probably already have a decent base of this from your research proposal , you need to expand on this substantially in the dissertation or thesis itself.

Essentially, you need to be looking for any existing literature that potentially helps you answer your research question (or develop it, if that’s not yet pinned down). There are numerous ways to find relevant literature, but I’ll cover my top four tactics here. I’d suggest combining all four methods to ensure that nothing slips past you:

Method 1 – Google Scholar Scrubbing

Google’s academic search engine, Google Scholar , is a great starting point as it provides a good high-level view of the relevant journal articles for whatever keyword you throw at it. Most valuably, it tells you how many times each article has been cited, which gives you an idea of how credible (or at least, popular) it is. Some articles will be free to access, while others will require an account, which brings us to the next method.

Method 2 – University Database Scrounging

Generally, universities provide students with access to an online library, which provides access to many (but not all) of the major journals.

So, if you find an article using Google Scholar that requires paid access (which is quite likely), search for that article in your university’s database – if it’s listed there, you’ll have access. Note that, generally, the search engine capabilities of these databases are poor, so make sure you search for the exact article name, or you might not find it.

Method 3 – Journal Article Snowballing

At the end of every academic journal article, you’ll find a list of references. As with any academic writing, these references are the building blocks of the article, so if the article is relevant to your topic, there’s a good chance a portion of the referenced works will be too. Do a quick scan of the titles and see what seems relevant, then search for the relevant ones in your university’s database.

Method 4 – Dissertation Scavenging

Similar to Method 3 above, you can leverage other students’ dissertations. All you have to do is skim through literature review chapters of existing dissertations related to your topic and you’ll find a gold mine of potential literature. Usually, your university will provide you with access to previous students’ dissertations, but you can also find a much larger selection in the following databases:

• Open Access Theses & Dissertations
• Stanford SearchWorks

Keep in mind that dissertations and theses are not as academically sound as published, peer-reviewed journal articles (because they’re written by students, not professionals), so be sure to check the credibility of any sources you find using this method. You can do this by assessing the citation count of any given article in Google Scholar. If you need help with assessing the credibility of any article, or with finding relevant research in general, you can chat with one of our Research Specialists .

Alright – with a good base of literature firmly under your belt, it’s time to move onto the next step.

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Step 2: Log, catalogue and synthesise

Once you’ve built a little treasure trove of articles, it’s time to get reading and start digesting the information – what does it all mean?

While I present steps one and two (hunting and digesting) as sequential, in reality, it’s more of a back-and-forth tango – you’ll read a little , then have an idea, spot a new citation, or a new potential variable, and then go back to searching for articles. This is perfectly natural – through the reading process, your thoughts will develop , new avenues might crop up, and directional adjustments might arise. This is, after all, one of the main purposes of the literature review process (i.e. to familiarise yourself with the current state of research in your field).

As you’re working through your treasure chest, it’s essential that you simultaneously start organising the information. There are three aspects to this:

• Logging reference information
• Building an organised catalogue
• Distilling and synthesising the information

I’ll discuss each of these below:

2.1 – Log the reference information

As you read each article, you should add it to your reference management software. I usually recommend Mendeley for this purpose (see the Mendeley 101 video below), but you can use whichever software you’re comfortable with. Most importantly, make sure you load EVERY article you read into your reference manager, even if it doesn’t seem very relevant at the time.

2.2 – Build an organised catalogue

In the beginning, you might feel confident that you can remember who said what, where, and what their main arguments were. Trust me, you won’t. If you do a thorough review of the relevant literature (as you must!), you’re going to read many, many articles, and it’s simply impossible to remember who said what, when, and in what context . Also, without the bird’s eye view that a catalogue provides, you’ll miss connections between various articles, and have no view of how the research developed over time. Simply put, it’s essential to build your own catalogue of the literature.

I would suggest using Excel to build your catalogue, as it allows you to run filters, colour code and sort – all very useful when your list grows large (which it will). How you lay your spreadsheet out is up to you, but I’d suggest you have the following columns (at minimum):

• Author, date, title – Start with three columns containing this core information. This will make it easy for you to search for titles with certain words, order research by date, or group by author.
• Categories or keywords – You can either create multiple columns, one for each category/theme and then tick the relevant categories, or you can have one column with keywords.
• Key arguments/points – Use this column to succinctly convey the essence of the article, the key arguments and implications thereof for your research.
• Context – Note the socioeconomic context in which the research was undertaken. For example, US-based, respondents aged 25-35, lower- income, etc. This will be useful for making an argument about gaps in the research.
• Methodology – Note which methodology was used and why. Also, note any issues you feel arise due to the methodology. Again, you can use this to make an argument about gaps in the research.
• Quotations – Note down any quoteworthy lines you feel might be useful later.
• Notes – Make notes about anything not already covered. For example, linkages to or disagreements with other theories, questions raised but unanswered, shortcomings or limitations, and so forth.

If you’d like, you can try out our free catalog template here (see screenshot below).

2.3 – Digest and synthesise

Most importantly, as you work through the literature and build your catalogue, you need to synthesise all the information in your own mind – how does it all fit together? Look for links between the various articles and try to develop a bigger picture view of the state of the research. Some important questions to ask yourself are:

• What answers does the existing research provide to my own research questions ?
• Which points do the researchers agree (and disagree) on?
• How has the research developed over time?
• Where do the gaps in the current research lie?

To help you develop a big-picture view and synthesise all the information, you might find mind mapping software such as Freemind useful. Alternatively, if you’re a fan of physical note-taking, investing in a large whiteboard might work for you.

Step 3: Outline and write it up!

Once you’re satisfied that you have digested and distilled all the relevant literature in your mind, it’s time to put pen to paper (or rather, fingers to keyboard). There are two steps here – outlining and writing:

3.1 – Draw up your outline

Having spent so much time reading, it might be tempting to just start writing up without a clear structure in mind. However, it’s critically important to decide on your structure and develop a detailed outline before you write anything. Your literature review chapter needs to present a clear, logical and an easy to follow narrative – and that requires some planning. Don’t try to wing it!

Naturally, you won’t always follow the plan to the letter, but without a detailed outline, you’re more than likely going to end up with a disjointed pile of waffle , and then you’re going to spend a far greater amount of time re-writing, hacking and patching. The adage, “measure twice, cut once” is very suitable here.

In terms of structure, the first decision you’ll have to make is whether you’ll lay out your review thematically (into themes) or chronologically (by date/period). The right choice depends on your topic, research objectives and research questions, which we discuss in this article .

Once that’s decided, you need to draw up an outline of your entire chapter in bullet point format. Try to get as detailed as possible, so that you know exactly what you’ll cover where, how each section will connect to the next, and how your entire argument will develop throughout the chapter. Also, at this stage, it’s a good idea to allocate rough word count limits for each section, so that you can identify word count problems before you’ve spent weeks or months writing!

PS – check out our free literature review chapter template…

3.2 – Get writing

With a detailed outline at your side, it’s time to start writing up (finally!). At this stage, it’s common to feel a bit of writer’s block and find yourself procrastinating under the pressure of finally having to put something on paper. To help with this, remember that the objective of the first draft is not perfection – it’s simply to get your thoughts out of your head and onto paper, after which you can refine them. The structure might change a little, the word count allocations might shift and shuffle, and you might add or remove a section – that’s all okay. Don’t worry about all this on your first draft – just get your thoughts down on paper.

Once you’ve got a full first draft (however rough it may be), step away from it for a day or two (longer if you can) and then come back at it with fresh eyes. Pay particular attention to the flow and narrative – does it fall fit together and flow from one section to another smoothly? Now’s the time to try to improve the linkage from each section to the next, tighten up the writing to be more concise, trim down word count and sand it down into a more digestible read.

Once you’ve done that, give your writing to a friend or colleague who is not a subject matter expert and ask them if they understand the overall discussion. The best way to assess this is to ask them to explain the chapter back to you. This technique will give you a strong indication of which points were clearly communicated and which weren’t. If you’re working with Grad Coach, this is a good time to have your Research Specialist review your chapter.

Finally, tighten it up and send it off to your supervisor for comment. Some might argue that you should be sending your work to your supervisor sooner than this (indeed your university might formally require this), but in my experience, supervisors are extremely short on time (and often patience), so, the more refined your chapter is, the less time they’ll waste on addressing basic issues (which you know about already) and the more time they’ll spend on valuable feedback that will increase your mark-earning potential.

Literature Review Example

In the video below, we unpack an actual literature review so that you can see how all the core components come together in reality.

Let’s Recap

In this post, we’ve covered how to research and write up a high-quality literature review chapter. Let’s do a quick recap of the key takeaways:

• It is essential to understand the WHY of the literature review before you read or write anything. Make sure you understand the 4 core functions of the process.
• The first step is to hunt down the relevant literature . You can do this using Google Scholar, your university database, the snowballing technique and by reviewing other dissertations and theses.
• Next, you need to log all the articles in your reference manager , build your own catalogue of literature and synthesise all the research.
• Following that, you need to develop a detailed outline of your entire chapter – the more detail the better. Don’t start writing without a clear outline (on paper, not in your head!)
• Write up your first draft in rough form – don’t aim for perfection. Remember, done beats perfect.
• Refine your second draft and get a layman’s perspective on it . Then tighten it up and submit it to your supervisor.

Psst… there’s more!

This post is an extract from our bestselling Udemy Course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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38 Comments

Thank you very much. This page is an eye opener and easy to comprehend.

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But all the same I’ll make use of this opportunity to the fullest.

Thank you for this good job.

Keep it up!

You’re welcome, Yinka. Thank you for the kind words. All the best writing your literature review.

Thank you for a very useful literature review session. Although I am doing most of the steps…it being my first masters an Mphil is a self study and one not sure you are on the right track. I have an amazing supervisor but one also knows they are super busy. So not wanting to bother on the minutae. Thank you.

You’re most welcome, Renee. Good luck with your literature review 🙂

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You’re welcome, Maithe. Good luck writing your literature review 🙂

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How to Write a Literature Review

What is a literature review.

• What Is the Literature
• Writing the Review

A literature review is much more than an annotated bibliography or a list of separate reviews of articles and books. It is a critical, analytical summary and synthesis of the current knowledge of a topic. Thus it should compare and relate different theories, findings, etc, rather than just summarize them individually. In addition, it should have a particular focus or theme to organize the review. It does not have to be an exhaustive account of everything published on the topic, but it should discuss all the significant academic literature and other relevant sources important for that focus.

This is meant to be a general guide to writing a literature review: ways to structure one, what to include, how it supplements other research. For more specific help on writing a review, and especially for help on finding the literature to review, sign up for a Personal Research Session .

The specific organization of a literature review depends on the type and purpose of the review, as well as on the specific field or topic being reviewed. But in general, it is a relatively brief but thorough exploration of past and current work on a topic. Rather than a chronological listing of previous work, though, literature reviews are usually organized thematically, such as different theoretical approaches, methodologies, or specific issues or concepts involved in the topic. A thematic organization makes it much easier to examine contrasting perspectives, theoretical approaches, methodologies, findings, etc, and to analyze the strengths and weaknesses of, and point out any gaps in, previous research. And this is the heart of what a literature review is about. A literature review may offer new interpretations, theoretical approaches, or other ideas; if it is part of a research proposal or report it should demonstrate the relationship of the proposed or reported research to others' work; but whatever else it does, it must provide a critical overview of the current state of research efforts. 

Literature reviews are common and very important in the sciences and social sciences. They are less common and have a less important role in the humanities, but they do have a place, especially stand-alone reviews.

Types of Literature Reviews

There are different types of literature reviews, and different purposes for writing a review, but the most common are:

• Stand-alone literature review articles . These provide an overview and analysis of the current state of research on a topic or question. The goal is to evaluate and compare previous research on a topic to provide an analysis of what is currently known, and also to reveal controversies, weaknesses, and gaps in current work, thus pointing to directions for future research. You can find examples published in any number of academic journals, but there is a series of Annual Reviews of *Subject* which are specifically devoted to literature review articles. Writing a stand-alone review is often an effective way to get a good handle on a topic and to develop ideas for your own research program. For example, contrasting theoretical approaches or conflicting interpretations of findings can be the basis of your research project: can you find evidence supporting one interpretation against another, or can you propose an alternative interpretation that overcomes their limitations?
• Part of a research proposal . This could be a proposal for a PhD dissertation, a senior thesis, or a class project. It could also be a submission for a grant. The literature review, by pointing out the current issues and questions concerning a topic, is a crucial part of demonstrating how your proposed research will contribute to the field, and thus of convincing your thesis committee to allow you to pursue the topic of your interest or a funding agency to pay for your research efforts.
• Part of a research report . When you finish your research and write your thesis or paper to present your findings, it should include a literature review to provide the context to which your work is a contribution. Your report, in addition to detailing the methods, results, etc. of your research, should show how your work relates to others' work.

A literature review for a research report is often a revision of the review for a research proposal, which can be a revision of a stand-alone review. Each revision should be a fairly extensive revision. With the increased knowledge of and experience in the topic as you proceed, your understanding of the topic will increase. Thus, you will be in a better position to analyze and critique the literature. In addition, your focus will change as you proceed in your research. Some areas of the literature you initially reviewed will be marginal or irrelevant for your eventual research, and you will need to explore other areas more thoroughly. 

Examples of Literature Reviews

See the series of Annual Reviews of *Subject* which are specifically devoted to literature review articles to find many examples of stand-alone literature reviews in the biomedical, physical, and social sciences. 

Research report articles vary in how they are organized, but a common general structure is to have sections such as:

• Abstract - Brief summary of the contents of the article
• Introduction - A explanation of the purpose of the study, a statement of the research question(s) the study intends to address
• Literature review - A critical assessment of the work done so far on this topic, to show how the current study relates to what has already been done
• Methods - How the study was carried out (e.g. instruments or equipment, procedures, methods to gather and analyze data)
• Results - What was found in the course of the study
• Discussion - What do the results mean
• Conclusion - State the conclusions and implications of the results, and discuss how it relates to the work reviewed in the literature review; also, point to directions for further work in the area

Here are some articles that illustrate variations on this theme. There is no need to read the entire articles (unless the contents interest you); just quickly browse through to see the sections, and see how each section is introduced and what is contained in them.

The Determinants of Undergraduate Grade Point Average: The Relative Importance of Family Background, High School Resources, and Peer Group Effects , in The Journal of Human Resources , v. 34 no. 2 (Spring 1999), p. 268-293.

This article has a standard breakdown of sections:

• Introduction
• Literature Review
• Some discussion sections

First Encounters of the Bureaucratic Kind: Early Freshman Experiences with a Campus Bureaucracy , in The Journal of Higher Education , v. 67 no. 6 (Nov-Dec 1996), p. 660-691.

This one does not have a section specifically labeled as a "literature review" or "review of the literature," but the first few sections cite a long list of other sources discussing previous research in the area before the authors present their own study they are reporting.

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• Last Updated: Jan 11, 2024 9:48 AM
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• 04 December 2020
• Correction 09 December 2020

How to write a superb literature review

Andy Tay is a freelance writer based in Singapore.

You can also search for this author in PubMed   Google Scholar

Literature reviews are important resources for scientists. They provide historical context for a field while offering opinions on its future trajectory. Creating them can provide inspiration for one’s own research, as well as some practice in writing. But few scientists are trained in how to write a review — or in what constitutes an excellent one. Even picking the appropriate software to use can be an involved decision (see ‘Tools and techniques’). So Nature asked editors and working scientists with well-cited reviews for their tips.

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Correction 09 December 2020 : An earlier version of the tables in this article included some incorrect details about the programs Zotero, Endnote and Manubot. These have now been corrected.

Hsing, I.-M., Xu, Y. & Zhao, W. Electroanalysis 19 , 755–768 (2007).

Article   Google Scholar  

Ledesma, H. A. et al. Nature Nanotechnol. 14 , 645–657 (2019).

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How to Do a Literature Review: Introduction

• Introduction
• Where to Begin
• Organization & Writing

What Is a Literature Review?

A literature review looks at key published material (scholarly articles, books, pamphlets, etc.) on a particular issue, area of research, or theory and provides not only a summary of the source, but also a critical evaluation.  Each source is summarized, synthesized, and often evaluated.  More than a mere summary of the sources, it highlights what is and is not known, identifies controversy surrounding a topic, formulates questions that need further research, linking the known literature to how your research adds to the larger field of study.

A literature review can be part of a larger research project in which the researcher presents a proposal, plan of action, or primary research work (a survey, interviews); or, it can stand alone as an analysis of what the experts say on a given issue or area. 

For a quick overview, watch this excellent video: What is a Literature Review?  by Steely Libraries NKU.

Types of Literature Reviews

Systematic reviews  are literature reviews structured by an explicit purpose and a set of specific parameters regarding the sources reviewed.  They contain:

• a specific problem for which the review is being performed
• one or more research purposes/questions targeting that problem
• the sources of research that will be reviewed
• specifics on the search process
• specific metrics for selecting sources
• techniques used to evaluate the sources
• techniques used to analyze and synthesize the findings in the sources

Meta-analyses:  Systematic reviews which use a quantitative way of statistically summarizing and comparing the results of the studies reviewed.

Argumentative Review :  Literature reviews that support or oppose an argument, assumption, or problem established within the literature

Integrative Review : A review that synthesizes the literature such that new perspectives on the topic are introduced.

Historical Review : Looks at research throughout a time period, examining trends, evolution, developments--often pointing to future direction for research.

Methodological Review : Reviews the method of analyses used in studies--can highlight problems, ethical issues to be aware of in research to be conducted.

Theoretical Review : Looks at theories surrounding a concept/issue/phenomena establishing current thinking, degree of investigation regarding the theories, relationships between them, shortcomings, or emerging research problems unanswered by current theories.

Why Create a Literature Review?

A literature review:

• provides an overview of established knowledge and ideas directly related to and organized around a specific research question
• provides professionals with a guide to the literature
• provides context and background for a research question
• provides credibility for the author's knowledge of the field
• helps to establish underpinnings behind the research are factual
• helps identify previous areas of scholarship to prevent duplication of research

How Is a Literature Review Different from an Annotated Bibliography?

Literature reviews and annotated bibliographies are close cousins, but there are many differences between the two.

This short video gives an excellent account of what an annotated bibliography involves: What's an Annotated Bibliography , Brock University Library.

They have in common that they both focus primarily on published materials, usually scholarly, that present a range of perspectives on a specific topic.

They differ as follows:

Note: Both the literature review and the annotated bibliography are excellent tools for getting the most out of your research. For this reason, your professor may sometimes ask you to complete the literature review section of your Constructive Action (CA) project as an annotated bibliography.

• Next: Where to Begin >>
• Last Updated: Mar 4, 2021 10:44 AM
• URL: https://libguides.mcny.edu/literaturereview

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 
• How to write a good literature review 
• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

• Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 
• Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 
• Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 
• Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 
• Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 
• Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

How to write a good literature review

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. 

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

Paperpal is an AI writing assistant that help academics write better, faster with real-time suggestions for in-depth language and grammar correction. Trained on millions of research manuscripts enhanced by professional academic editors, Paperpal delivers human precision at machine speed.  

Try it for free or upgrade to  Paperpal Prime , which unlocks unlimited access to premium features like academic translation, paraphrasing, contextual synonyms, consistency checks and more. It’s like always having a professional academic editor by your side! Go beyond limitations and experience the future of academic writing.  Get Paperpal Prime now at just US$19 a month!

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• Empirical Research: A Comprehensive Guide for Academics 
• How to Write a Scientific Paper in 10 Steps 
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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Conducting a Literature Review

• Introduction

What is a Literature Review?

Goals of the literature review, types of literature reviews, recommended reading.

• Planning Your Literature Review
• Choose Keywords
• Decide where to search
• Formulate Your Search Strategy
• Utilize Citation Chaining
• When to Stop Searching
• Using Ai for Searching the Literature
• Evaluate, Synthesize & Analyze the Literature
• Write a Literature Review

A literature review surveys, summarizes, critically analyzes, compares, and synthesizes multiple scholarly works, or published knowledge on a particular topic or specific subject area.

Literature can include peer-reviewed or scholarly  articles, books/ ebooks, conference proceedings, theses/ dissertations, documents published by governmental agencies and non-profit organizations, and other forms of gray literature.

Conducting a literature review is part of the research process and serves to establish a base of knowledge and overview of the principal works on a specific area of research as well as identify important themes, discoveries, areas of consensus and debate, changes over time, and provide a foundation for further research.

A literature review may be written to:

•     Synthesize past and current literature on a topic
•     Identify a problem in a field of research  
•     Show how the literature relates to one another
•     Place your work in the the context of other related research

What kinds of sources require a Literature Review?

•     A thesis or dissertation
•     A grant proposal
•     A research paper assigned in a course 
•     An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

The following are common types of literature reviews:

Narrative or Traditional Review

The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

Systematic Review

The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find.

Meta-analysis

This type of review utilizes quantitative methods to combine the results of independent studies and synthesize summaries and conclusions which can be used to evaluate therapeutic effectiveness, plan new studies, etc.

Meta-synthesis

A meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic.

Further Reading on Different Types of Literature Reviews

Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies . Health Information and Libraries Journal, 26(2), 91-108. doi:10.1111/j.1471-1842.2009.00848.x Gough, D., Thomas, J., & Oliver, S. (2012). Clarifying differences between review designs and methods . Systematic Reviews, 1, 28. doi:10.1186/2046-4053-1-28

The library has a number of books on conducting and writing literature reviews. The following are some recommended ebooks available in the library:

Books on Conducting Systematic Literature Reviews:

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Introduction to Literature Reviews

Introduction.

• Step One: Define
• Step Two: Research
• Step Three: Write
• Suggested Readings

A literature review is a written work that :

• Compiles significant research published on a topic by accredited scholars and researchers;
• —Surveys scholarly articles, books, dissertations, conference proceedings, and other sources;
• —Examines contrasting perspectives, theoretical approaches, methodologies, findings, results, conclusions.
• —Reviews critically, analyzes, and synthesizes existing research on a topic; and,
• Performs a thorough “re” view, “overview”, or “look again” of past and current works on a subject, issue, or theory.

From these analyses, the writer then offers an overview of the current status of a particular area of knowledge from both a practical and theoretical perspective.

Literature reviews are important because they are usually a  required  step in a thesis proposal (Master's or PhD). The proposal will not be well-supported without a literature review. Also, literature reviews are important because they help you learn important authors and ideas in your field. This is useful for your coursework and your writing. Knowing key authors also helps you become acquainted with other researchers in your field.

Look at this diagram and imagine that your research is the "something new." This shows how your research should relate to major works and other sources.

Olivia Whitfield | Graduate Reference Assistant | 2012-2015

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Literature Reviews

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What is a literature review?

A literature review discusses published information in a particular subject area. Often part of the introduction to an essay, research report or thesis, the literature review is literally a "re" view or "look again" at what has already been written about the topic, wherein the author analyzes a segment of a published body of knowledge through summary, classification, and comparison of prior research studies, reviews of literature, and theoretical articles. Literature reviews provide the reader with a bibliographic history of the scholarly research in any given field of study. As such,  as new information becomes available, literature reviews grow in length or become focused on one specific aspect of the topic.

A literature review can be just a simple summary of the sources, but usually contains an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, whereas a synthesis is a re-organization, or a reshuffling, of that information. The literature review might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. Depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

A literature review is NOT:

• An annotated bibliography – a list of citations to books, articles and documents that includes a brief description and evaluation for each citation. The annotations inform the reader of the relevance, accuracy and quality of the sources cited.
• A literary review – a critical discussion of the merits and weaknesses of a literary work.
• A book review – a critical discussion of the merits and weaknesses of a particular book.
• Teaching Information Literacy Reframed: 50+ Framework-Based Exercises for Creating Information-Literate Learners
• The UNC Writing Center – Literature Reviews
• The UW-Madison Writing Center: The Writer’s Handbook – Academic and Professional Writing – Learn How to Write a Literature Review

What is the difference between a literature review and a research paper?

The focus of a literature review is to summarize and synthesize the arguments and ideas of others without adding new contributions, whereas academic research papers present and develop new arguments that build upon the previously available body of literature.

How do I write a literature review?

There are many resources that offer step-by-step guidance for writing a literature review, and you can find some of them under Other Resources in the menu to the left. Writing the Literature Review: A Practical Guide suggests these steps:

• Chose a review topic and develop a research question
• Locate and organize research sources
• Select, analyze and annotate sources
• Evaluate research articles and other documents
• Structure and organize the literature review
• Develop arguments and supporting claims
• Synthesize and interpret the literature
• Put it all together

What is the purpose of writing a literature review?

Literature reviews serve as a guide to a particular topic: professionals can use literature reviews to keep current on their field; scholars can determine credibility of the writer in his or her field by analyzing the literature review.

As a writer, you will use the literature review to:

• See what has, and what has not, been investigated about your topic
• Identify data sources that other researches have used
• Learn how others in the field have defined and measured key concepts
• Establish context, or background, for the argument explored in the rest of a paper
• Explain what the strengths and weaknesses of that knowledge and ideas might be
• Contribute to the field by moving research forward
• To keep the writer/reader up to date with current developments in a particular field of study
• Develop alternative research projects
• Put your work in perspective
• Demonstrate your understanding and your ability to critically evaluate research in the field
• Provide evidence that may support your own findings
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Preparing to Write the Literature Review: Introduction

• Introduction
• Keyword Search vs. Subject Search
• Advanced Searching PlayList

If You Are New to Research

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What is the "Literature"?

The "literature" is the body of scholarly work in any given field.

If your browser does not display frames, please use the direct link to the video provided on this page.

• What is the "Literature"? Direct link to video tutorial.

What is a Literature Review?

A literature review surveys scholarly articles, books, dissertations, and conference proceedings relevant to your research problem, providing a description, summary, and critical evaluation of each work.

Purpose of the literature review:

• Provides a historical background for your research problem
• Describes its current status
• Supports the purpose of the study
• Identifies gaps in the literature
• Become aware of variables relevant to the problem
• Understand the seminal studies widely cited
• Identifies the leading scholars relevant to the problem  

(Lunenburg, 2008)

Things to Know

Three important things to know about research

• Start early: the library has thousands of books and articles online. If we don’t have what you need, we will get it for you, but this process takes about a week.
• Be prepared: bring a flash drive with you always so you can save what you find, OR use a citation manager.
• Take notes about how you found your results! Maybe keep a “research journal.”

Literature Reviews vs. Original Research

Nearly every scholarly research article begins with a brief, basic review of existing literature. This review introduces the subject being investigated and what is already known about it, in order to provide context for the author's new research.

Check the "Introduction" section of this original research article for an example: 

• Characterisation of Mainstream and Passive Vapors Emitted by Selected Electronic Cigarettes

There is also a whole category of scholarly articles known as literature reviews. (Generally, these will use words like "Literature Review," "Review," or "Review of the Literature" right in the title.) These articles do not conduct new research, but only review existing research on some subject, in order to summarize the current state of knowledge and help other researchers exploring the same topic.

An example of a Literature Review article:

• "Inner Ear Damage Following Electric Current and Lightning Injury: a Literature Review"

Ask Your Instructor

If you have any of these questions

How far back should you look?

How many sources should you have?

What kinds of sources should you use?

Ask your instructor! Different departments have different requirements.

Research Tools

• Databases by Subject The library has nearly 100 databases. Use this page to see the databases that are most appropriate for your subject.
• Library Catalog (OneSearch: Books & Media CSUSB) The library catalog lists everything in the library's collection. It will tell you the floor location and the call number.
• Citation Finder Use this tool to find out if the library has the journal you need. You'll need at least the journal name and the year.
• Interlibrary Loan Requests This link opens in a new window If the library doesn't have what you need, we will get it for you. You'll need to provide the citation information.
• APA Citation Library Guide
• Zotero Library Guide

Tips on writing...

• Writing Literature Reviews (UNC)
• The Literature Review: A Few Tips On Conducting It
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• 1. Let's Get Writing
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• 3.2. Crafts and Puzzles
• 3.3. The Papers Trail
• 3.4. The Fine Art of Sentencing
• 3.5. Hurdles
• 3.6. Small Stressors
• 4. Literature Reviews
• 4.1. Introduction to Literature Reviews
• 4.2. What is a Literature Review?
• 4.3. How to Get Started
• 4.4. Where to Find the Literature
• 4.5. Evaluating Sources
• 4.6. Documenting Sources
• 4.7. Synthesizing Sources
• 4.8. Writing the Literature Review
• 4.9. Concluding Thoughts on Literature Reviews
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Introduction to Literature Reviews

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Learning Objectives

At the conclusion of this chapter, you will be able to:

• Identify the purpose of the literature review in  the research process;
• Distinguish between different types of literature reviews.

What is a Literature Review?

Pick up nearly any book on research methods and you will find a description of a literature review.  At a basic level, the term implies a survey of factual or nonfiction books, articles, and other documents published on a particular subject.  Definitions may be similar across the disciplines, with new types and definitions continuing to emerge.  Generally speaking, a literature review is a:

• “comprehensive background of the literature within the interested topic area…” ( O’Gorman & MacIntosh, 2015, p. 31 [https://edtechbooks.org/-EaoJ] ).
• “critical component of the research process that provides an in-depth analysis of recently published research findings in specifically identified areas of interest.” ( House, 2018, p. 109 [https://edtechbooks.org/-EaoJ] ).
• “written document that presents a logically argued case founded on a comprehensive understanding of the current state of knowledge about a topic of study” ( Machi & McEvoy,  2012, p. 4 [https://edtechbooks.org/-EaoJ] ).

As a foundation for knowledge advancement in every discipline, it is an important element of any research project.  At the graduate or doctoral level, the literature review is an essential feature of thesis and dissertation, as well as grant proposal writing.  That is to say, “A substantive, thorough, sophisticated literature review is a precondition for doing substantive, thorough, sophisticated research…A researcher cannot perform significant research without first understanding the literature in the field.” ( Boote & Beile, 2005, p. 3 [https://edtechbooks.org/-EaoJ] ).  It is by this means, that a researcher demonstrates familiarity with a body of knowledge and thereby establishes credibility with a reader.  An advanced-level literature review shows how prior research is linked to a new project, summarizing and synthesizing what is known while identifying gaps in the knowledge base, facilitating theory development, closing areas where enough research already exists, and uncovering areas where more research is needed. ( Webster & Watson, 2002, p. xiii [https://edtechbooks.org/-EaoJ] )

A graduate-level literature review is a compilation of the most significant previously published research on your topic. Unlike an annotated bibliography or a research paper you may have written as an undergraduate, your literature review will outline, evaluate and synthesize relevant research and relate those sources to your own thesis or research question. It is much more than a summary of all the related literature.

It is a type of writing that demonstrate the importance of your research by defining the main ideas and the relationship between them. A good literature review lays the foundation for the importance of your stated problem and research question.

Literature reviews do the following:

• define a concept
• map the research terrain or scope
• systemize relationships between concepts
• identify gaps in the literature ( Rocco & Plathotnik, 2009, p. 128 [https://edtechbooks.org/-EaoJ] )

In the context of a research study, the purpose of a literature review is to demonstrate that your research question  is meaningful. Additionally, you may review the literature of different disciplines to find deeper meaning and understanding of your topic. It is especially important to consider other disciplines when you do not find much on your topic in one discipline. You will need to search the cognate literature before claiming there is “little previous research” on your topic.

Well developed literature reviews involve numerous steps and activities. The literature review is an iterative process because you will do at least two of them: a preliminary search to learn what has been published in your area and whether there is sufficient support in the literature for moving ahead with your subject. After this first exploration, you will conduct a deeper dive into the literature to learn everything you can about the topic and its related issues.

Literature Review Tutorial

Literature Review Basics

An effective literature review must:

• Methodologically analyze and synthesize quality literature on a topic
• Provide a firm foundation to a topic or research area
• Provide a firm foundation for the selection of a research methodology
• Demonstrate that the proposed research contributes something new to the overall body of knowledge of advances the research field’s knowledge base. ( Levy & Ellis, 2006 [https://edtechbooks.org/-EaoJ] ).

All literature reviews, whether they are qualitative, quantitative or both, will at some point:

• Introduce the topic and define its key terms
• Establish the importance of the topic
• Provide an overview of the amount of available literature and its types (for example: theoretical, statistical, speculative)
• Identify gaps in the literature
• Point out consistent finding across studies
• Arrive at a synthesis that organizes what is known about a topic
• Discusses possible implications and directions for future research

Types of Literature Reviews

There are many different types of literature reviews, however there are some shared characteristics or features that all share.  Remember a comprehensive literature review is, at its most fundamental level, an original work based on an extensive critical examination and synthesis of the relevant literature on a topic. As a study of the research on a particular topic, it is arranged by key themes or findings, which may lead up to or link to the  research question.  In some cases, the research question will drive the type of literature review that is undertaken.

The following section includes brief descriptions of the terms used to describe different literature review types with examples of each.   The included citations are open access, Creative Commons licensed or copyright-restricted.

Guided by an understanding of basic issues rather than a research methodology, the writer of a conceptual literature review is looking for key factors, concepts or variables and the presumed relationship between them. The goal of the conceptual literature review is to categorize and describe concepts relevant to the study or topic and outline a relationship between them, including relevant theory and empirical research.

Examples of a Conceptual Review:

• The formality of learning science in everyday life: A conceptual literature review ( Dohn, 2010 [https://edtechbooks.org/-EaoJ] ).
• Are we asking the right questions? A conceptual review of the educational development literature in higher education ( Amundsen & Wilson, 2012 [https://edtechbooks.org/-EaoJ] ).

An empirical literature review collects, creates, arranges, and analyzes numeric data reflecting the frequency of themes, topics, authors and/or methods found in existing literature. Empirical literature reviews present their summaries in quantifiable terms using descriptive and inferential statistics.

Examples of an Empirical Review:

• Impediments of e-learning adoption in higher learning institutions of Tanzania: An empirical review ( Mwakyusa & Mwalyagile, 2016 [https://edtechbooks.org/-EaoJ] ).
• Exploratory

The purpose of an exploratory review is to provide a broad approach to the topic area. The aim is breadth rather than depth and to get a general feel for the size of the topic area. A graduate student might do an exploratory review of the literature before beginning a more comprehensive one (e.g., synoptic).

Examples of an Exploratory Review:

• University research management: An exploratory literature review ( Schuetzenmeister, 2010 [https://edtechbooks.org/-EaoJ] ).
• An exploratory review of design principles in constructivist gaming learning environments ( Rosario & Widmeyer, 2009 [https://edtechbooks.org/-EaoJ] ).

This type of literature review is limited to a single aspect of previous research, such as methodology. A focused literature review generally will describe the implications of choosing a particular element of past research, such as methodology in terms of data collection, analysis, and interpretation.

Examples of a Focused Review:

• Language awareness: Genre awareness-a focused review of the literature ( Stainton, 1992 [https://edtechbooks.org/-EaoJ] ).

Integrative

An integrative review critiques past research and draws overall conclusions from the body of literature at a specified point in time. As such, it reviews, critiques, and synthesizes representative literature on a topic in an integrated way. Most integrative reviews may require the author to adopt a guiding theory, a set of competing models, or a point of view about a topic.  For more description of integrative reviews, see Whittemore & Knafl (2005) [https://edtechbooks.org/-EaoJ] .

Examples of an Integrative Review:

• Exploring the gap between teacher certification and permanent employment in Ontario: An integrative literature review ( Brock & Ryan, 2016 [https://edtechbooks.org/-EaoJ] ).
• Meta-analysis

A subset of a systematic review, a meta-analysis takes findings from several studies on the same subject and analyzes them using standardized statistical procedures to pool together data. As such, it integrates findings from a large body of quantitative findings to enhance understanding, draw conclusions, and detect patterns and relationships. By gathering data from many different, independent studies that look at the same research question and assess similar outcome measures, data can be combined and re-analyzed, providing greater statistical power than any single study alone. It’s important to note that not every systematic review includes a meta-analysis but a meta-analysis can’t exist without a systematic review of the literature.

Examples of a Meta-Analysis:

• Efficacy of the cooperative learning method on mathematics achievement and attitude: A meta-analysis research ( Capar & Tarim, 2015 [https://edtechbooks.org/-EaoJ] ).
• Gender differences in student attitudes toward science: A meta-analysis of the literature from 1970 to 1991 ( Weinburgh, 1995 [https://edtechbooks.org/-EaoJ] ).

Narrative/Traditional

A narrative or traditional review provides an overview of research on a particular topic that critiques and summarizes a body of literature. Typically broad in focus, these reviews select and synthesize relevant past research into a coherent discussion. Methodologies, findings and limits of the existing body of knowledge are discussed in narrative form. This requires a sufficiently focused research question, and the process may be subject to bias that supports the researcher’s own work.

Examples of a Narrative/Traditional Review:

• Adventure education and Outward Bound: Out-of-class experiences that make a lasting difference ( Hattie, Marsh, Neill, & Richards, 1997 [https://edtechbooks.org/-EaoJ] ).
• Good quality discussion is necessary but not sufficient in asynchronous tuition: A brief narrative review of the literature ( Fear & Erikson-Brown, 2014 [https://edtechbooks.org/-EaoJ] ).

This specific type of literature review is theory-driven and interpretative and is intended to explain the outcomes of a complex intervention program(s).

Examples of a Realist Review:

• Unravelling quality culture in higher education: A realist review ( Bendermacher, Egbrink, Wolfhagen, & Dolmans, 2017 [https://edtechbooks.org/-EaoJ] ).

This type of review tends to be a non-systematic approach that focuses on breadth of coverage rather than depth. It utilizes a wide range of materials and may not evaluate the quality of the studies as much as count the number. Thus, it aims to identify the nature and extent of research in an area by providing a preliminary assessment of size and scope of available research and may also include research in progress.

Examples of a Scoping Review:

• Interdisciplinary doctoral research supervision: A scoping review ( Vanstone, Hibbert, Kinsella, McKenzie, Pitman, & Lingard, 2013 [https://edtechbooks.org/-EaoJ] ).

In contrast to an exploratory review, the purpose of a synoptic review is to provide a concise but accurate overview of all material that appears to be relevant to a chosen topic. Both content and methodological material is included. The review should aim to be both descriptive and evaluative as it summarizes previous studies while also showing how the body of literature could be extended and improved in terms of content and method by identifying gaps.

Examples of a Synoptic Review:

• Theoretical framework for educational assessment: A synoptic review ( Ghaicha, 2016 [https://edtechbooks.org/-EaoJ] ).
• School effects research: A synoptic review of past efforts and some suggestions for the future ( Cuttance, 1981 [https://edtechbooks.org/-EaoJ] ).

Systematic Review

A rigorous review that follows a strict methodology designed with a presupposed selection of literature reviewed, systematic reviews are undertaken to clarify the state of existing research, evidence, and possible implications that can be drawn.  Using comprehensive and exhaustive searching of the published and unpublished literature, searching various databases, reports, and grey literature, these reviews seek to produce transparent and reproducible results that report details of time frame and methods to minimize bias.  Generally, these reviews must include teams of at least 2-3 to allow for the critical appraisal of the literature.  For more description of systematic reviews, including links to protocols, checklists, workflow processes, and structure see “ A Young Researcher’s Guide to a Systematic Review [https://edtechbooks.org/-oF] “.

Examples of a Systematic Review:

• The potentials of using cloud computing in schools: A systematic literature review ( Hartmann, Braae, Pedersen, & Khalid, 2017 [https://edtechbooks.org/-EaoJ] ).
• The use of research to improve professional practice: a systematic review of the literature ( Hemsley-Brown & Sharp, 2003 [https://edtechbooks.org/-EaoJ] ).

Umbrella/Overview of Reviews

An umbrella review compiles evidence from multiple systematic reviews into one document. It therefore focuses on broad conditions or problems for which there are competing interventions and highlights reviews that address those interventions and their effects, thereby allowing for recommendations for practice. For a brief discussion see “ Not all literature reviews are the same [https://edtechbooks.org/-xZ] ” (Thomson, 2013).

Examples of an Umbrella/Overview Review:

• Reflective practice in healthcare education: An umbrella review ( Fragknos, 2016 [https://edtechbooks.org/-EaoJ] ).

Why do a Literature Review?

The purpose of the literature review is the same regardless of the topic or research method. It tests your own research question against what is already known about the subject.

First – It’s part of the whole.

Omission of a literature review chapter or section in a graduate-level project represents a serious void or absence of a critical element in the research process.

The outcome of your review is expected to demonstrate that you:

• can systematically explore the research in your topic area
• can read and critically analyze the literature in your discipline and then use it appropriately to advance your own work
• have sufficient knowledge in the topic to undertake further investigation

Second – It’s good for you!

• You improve your skills as a researcher
• You become familiar with the discourse of your discipline and learn how to be a scholar in your field
• You learn through writing your ideas and finding your voice in your subject area
• You define, redefine and clarify your research question for yourself in the process

Third – It’s good for your reader.

Your reader expects you to have done the hard work of gathering, evaluating, and synthesizing the literature.  When you do a literature review you:

• Set the context for the topic and present its significance
• Identify what’s important to know about your topic – including individual material, prior research, publications, organizations and authors.
• Demonstrate relationships among prior research
• Establish limitations of existing knowledge
• Analyze trends in the topic’s treatment and gaps in the literature

So, why should you do a literature review?

• To locate gaps in the literature of your discipline
• To avoid reinventing the wheel
• To carry on where others have already been
• To identify other people working in the same field
• To increase your breadth of knowledge in your subject area
• To find the seminal works in your field
• To provide intellectual context for your own work
• To acknowledge opposing viewpoints
• To put your work in perspective
• To demonstrate you can discover and retrieve previous work in the area

Common Literature Review Errors

Graduate-level literature reviews are more than a summary of the publications you find on a topic.  As you have seen in this brief introduction, literature reviews are a very specific type of research, analysis, and writing.  We will explore these topics more in the next chapters.  Some things to keep in mind as you begin your own research and writing are ways to avoid the most common errors seen in the first attempt at a literature review.  For a quick review of some of the pitfalls and challenges a new researcher faces when he/she begins work, see “ Get Ready: Academic Writing, General Pitfalls and (oh yes) Getting Started! [https://edtechbooks.org/-GUc] ”.

As you begin your own graduate-level literature review, try to avoid these common mistakes:

• Accepting another researcher’s finding as valid without evaluating methodology and data
• Ignoring contrary findings and alternative interpretations
• Providing findings that are not clearly related to one’s own study or that are too general
• Allowing insufficient time to defining best search strategies and writing
• Reporting rather than synthesizing isolated statistical results
• Choosing problematic or irrelevant keywords, subject headings and descriptors
• Relying too heavily on secondary sources
• Failing to transparently report search methods
• Summarizing rather than synthesizing articles

In conclusion, the purpose of a literature review is three-fold:

• to survey the current state of knowledge or evidence in the area of inquiry,
• to identify key authors, articles, theories, and findings in that area, and
• to identify gaps in knowledge in that research area.

A literature review is commonly done today using computerized keyword searches in online databases, often working with a trained librarian or information expert. Keywords can be combined using the Boolean operators, “and”, “or” and sometimes “not”  to narrow down or expand the search results. Once a list of articles is generated from the keyword and subject heading search, the researcher must then manually browse through each title and abstract, to determine the suitability of that article before a full-text article is obtained for the research question.

Literature reviews should be reasonably complete and not restricted to a few journals, a few years, or a specific methodology or research design. Reviewed articles may be summarized in the form of tables and can be further structured using organizing frameworks such as a concept matrix.

A well-conducted literature review should indicate whether the initial research questions have already been addressed in the literature, whether there are newer or more interesting research questions available, and whether the original research questions should be modified or changed in light of findings of the literature review.

The review can also provide some intuitions or potential answers to the questions of interest and/or help identify theories that have previously been used to address similar questions and may provide evidence to inform policy or decision-making ( Bhattacherjee, 2012 [https://edtechbooks.org/-EaoJ] ).

Test Yourself

The purpose of a graduate-level literature review is to summarize in as many words as possible everything that is known about my topic.

A literature review is significant because in the process of doing one, the researcher learns to read and critically assess the literature of a discipline and then uses it appropriately to advance his/her own research.

Read the following abstract and choose the correct type of literature review it represents.

The focus of this paper centers around timing associated with early childhood education programs and interventions using meta-analytic methods. At any given assessment age, a child’s current age equals starting age, plus duration of program, plus years since program ended. Variability in assessment ages across the studies should enable everyone to identify the separate effects of all three time-related components. The project is a meta-analysis of evaluation studies of early childhood education programs conducted in the United States and its territories between 1960 and 2007. The population of interest is children enrolled in early childhood education programs between the ages of 0 and 5 and their control-group counterparts. Since the data come from a meta-analysis, the population for this study is drawn from many different studies with diverse samples. Given the preliminary nature of their analysis, the authors cannot offer conclusions at this point. ( Duncan, Leak, Li, Magnuson, Schindler, & Yoshikawa, 2011 [https://edtechbooks.org/-EaoJ] ).

In this review, Mary Vorsino writes that she is interested in keeping the potential influences of women pragmatists of Dewey’s day in mind while presenting modern feminist re readings of Dewey. She wishes to construct a narrowly-focused and succinct literature review of thinkers who have donned a feminist lens to analyze Dewey’s approaches to education, learning, and democracy and to employ Dewey’s works in theorizing on gender and education and on gender in society. This article first explores Dewey as both an ally and a problematic figure in feminist literature and then investigates the broader sphere of feminist pragmatism and two central themes within it: (1) valuing diversity, and diverse experiences; and (2) problematizing fixed truths. ( Vorsino, 2015 [https://edtechbooks.org/-EaoJ] ).

Linda Frederiksen is the Head of Access Services at Washington State University Vancouver.  She has a Master of Library Science degree from Emporia State University in Kansas. Linda is active in local, regional and national organizations, projects and initiatives advancing open educational resources and equitable access to information.

Sue F. Phelps is the Health Sciences and Outreach Services Librarian at Washington State University Vancouver. Her research interests include information literacy, accessibility of learning materials for students who use adaptive technology, diversity and equity in higher education, and evidence based practice in the health sciences

Brigham Young University

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

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14 Writing a Literature Review: Introduction

Often the place where thesis students embark on their writing journey, the literature review is also the section where students can struggle the most.

What is a literature review?

A literature review provides an overview of the relevant work that has been done in a field and can be presented in a separate chapter in a traditional thesis, or as a section near the beginning of each publishable paper in a sandwich thesis.

The introduction chapter of a sandwich thesis may also contain a literature review that is broader in scope than those of the individual papers included.

The review of literature is a significant portion of most academic writing, as it orients both the researcher and the reader to what research has been done in an area to date (so as to avoid “re-inventing the wheel”), and also highlights gaps in current knowledge that the present research will seek to address. Literature reviews also indicate that the researcher is knowledgeable in their field, being an active member and participant in it. [1]

According to Kamler and Thomson (2006), there are six key tasks that must be accomplished by a literature review, as illustrated in the following poster. [2]

Why is writing the literature review so often a challenge?

The concept of “the literature review” itself is likely intimidating for graduate students, in part, because of the connotations the different parts of this title evoke when placed together.  First, “the” erroneously signifies that your literature review is one standalone thing, as opposed to something that is integrated and referred to throughout the entire thesis or article. A literature review should not simply be a separate piece completed at the beginning of the research/writing process and then only marginally edited at the end.

Second, the statement “the literature” also carries a potentially intimidating air about it. Literature signifies something of high culture and pretentious importance – impossible to attain, broad in scope, and just frustratingly out of reach.

Finally, “review” gives off the assumption that the reviewer is in the position of a passive audience member who looks on from the outside at all that is going on in the “literature” – not much activity or agency in this positioning.

Types of literature reviews

According to Arlene Fink (2014) in “Conducting Research Literature Reviews”, a literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by doing so, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic and to demonstrate to your readers how your research fits within a larger field of study.

The following table provides a comparison of the types of literature reviews you may encounter as a graduate student. [3]

Table 1: Types of literature reviews based on research approach

• Christine B. Feak and John M. Swales, Telling a Research Story: Writing a Literature Review (Michigan: The University of Michigan Press, 2009). ↵
• Barbara Kamler and Pat Thomson, Helping Doctoral Students Write: Pedagogies for Supervision (London: Routledge, 2006). ↵
• Maria Grant and Andrew Booth, “A typology of reviews: An analysis of 14 review types and associated methodologies,” Health Information and Libraries Journal 26.2 (2009): 91-108. ↵

McMaster University's Graduate Thesis Toolkit Copyright © 2021 by McMaster University is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

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University of Tasmania, Australia

Literature reviews.

• Introduction: who will benefit from this guide?
• Getting started: what is a literature review?
• How to develop a researchable question
• How to find the literature
• How to manage the reading and take notes that make sense
• How to bring it all together: examples, templates, links, guides

Who will benefit from this guide?

This guide is written for undergraduates and postgraduate, course work students who are doing their first literature review.

Higher degree research candidates and academic researchers, please also refer to the Resources for Researchers library guides for more detailed information on writing theses and systematic reviews. 

What is a literature review?

A literature review is an examination of research in a particular field. 

• It gathers, critically analyses, evaluates, and synthesises current research literature in a discipline,
• indicates where there may be strengths, gaps,  weaknesses, and agreements in the current research.

It considers:

• what has been done,
•  the current thinking,
• research trends,
•  principal debates,
• dominant ideas,
• methods used in researching the topic
• gaps and flaws in the research.

  http://libguides.lib.msu.edu/c.php?g=96146&p=904793

Different Types of reviews

You may be asked to complete a literature review that is done in a systematic way, that is like a systematic review.

Mostly, the literature review you will be asked to do will be integrative – that is, conclusions are drawn from the literature in order to create something new, such as a new hypothesis to address a question, a solution to a complex problem, a new workplace procedure or training program.

Some elements of what you are asked to do may be like a systematic review, particularly in health fields.

Systematic approach does not mean a systematic review.

A true systematic review is a complex research project:

•  conducted in a scientific manner,
• usually with more than one person involved,
• they take a long time to complete
• are generally a project in themselves.

For more information have a look at the Systematic Review library guide .

If you would like to know more about different types of reviews, have a look at the document below: 

At the core of a literature review is a synthesis of the research. 

While both analysis and synthesis are involved, s ynthesis goes beyond analysis and is a higher order thinking.(Bloom's taxonomy).

Looking at the diagram below, it is evident that synthesis goes well beyond just analysis. 

• Analysis asks you to break something down into its parts and compare and contrast with other research findings.
• where they agree and disagree
• the major themes, arguments, ideas in a field
• the questions raised and those yet to be answered.
• This will show the relationships between different aspects of the research findings in the literature.
• It is not a summary, but rather is organised around concepts and themes, where there is a combining of elements to form something new.

Watch this short clip from Utah State University which defines how to go about achieving synthesis. 

Synthesis: True or False. 

Quick Quiz: check your understanding of synthesis from the video by deciding which of these statements are true or false .

• Next: How to develop a researchable question >>
• Last Updated: Apr 10, 2024 11:56 AM
• URL: https://utas.libguides.com/literaturereviews

Literature Review Tips for the Introduction and Discussion Sections

A literature review is a summary of studies related to a particular area of research. It identifies and summarizes all the relevant research conducted on a particular topic. It is important that your literature review is focused . Therefore, you should choose a limited number of studies that are central to your topic rather than trying to collect a wide range of studies that might not be closely connected.

Literature reviews help you accomplish the following:

• Evaluate past research  Collecting relevant resources will help you see what research has already been done. This will also help avoid duplication.
• Identify experts It is important to identify credible researchers who have knowledge in a given field, in order to seek their help if you get stuck with certain aspects of your research.
• Identify key questions  Your ultimate aim is to bring something new to the conversation. Collecting resources will help you determine the important questions that need to be addressed.
• Determine methodologies used in past studies Knowing how others have approached a particular topic will give you the opportunity to identify problems and find new ways to research and study a topic. If the reported methodology was successful, you can use it and save time that you would otherwise be spending on optimization.

Presenting Literature Review in the Introduction and Discussion Sections

There are many benefits to presenting literature reviews in the introduction and discussion sections of your manuscripts . However, there are differences in how you can present literature reviews in each section.

What Should be Included in the Literature Review of the Introduction Section?

The literature reviewed in the introduction should:

• Introduce the topic
• Establish the significance of the study
• Provide an overview of the relevant literature
• Establish a context for the study using the literature
• Identify knowledge gaps
• Illustrate how the study will advance knowledge on the topic

As you can see, literature review plays a significant role in the introduction section. However, there are some things that you should avoid doing in this section. These include:

• Elaborating on the studies mentioned in the literature review
• Using studies from the literature review to aggressively support your research
• Directly quoting studies from the literature review

It is important to know how to integrate the literature review into the introduction in an effective way. Although you can mention other studies, they should not be the focus. Instead, focus on using the literature review to aid in setting a foundation for the manuscript.

What Goes in the Literature Review of the Discussion Section?

Literature reviews play an important role in the discussion section of a manuscript . In this section, your findings should be the focus, rather than those of other researchers. Therefore, you should only use the studies mentioned in the literature review as support and evidence for your study.

There are three ways in which you can use literature reviews in the discussion section:

• To Provide Context for Your Study Using studies from the literature review helps to set the foundation for how you will reveal your findings and develop your ideas.
• Compare your Findings to Other Studies You can use previous literature as a backdrop to compare your new findings. This helps describe and also advance your ideas.
• State the Contribution of Your Study In addition to developing your ideas, you can use literature reviews to explain how your study contributes to the field of study.

However, there are three common mistakes that researchers make when including literature reviews in the discussion section. First, they mention all sorts of studies, some of which are not even relevant to the topic under investigation. Second, instead of citing the original article, they cite a related article that mentions the original article. Lastly, some authors cite previous work solely based on the abstract, without even going through the entire paper.

We hope this article helps you effectively present your literature review in both the introduction as well as the discussion section of your manuscript. You can also mention any other tips that will add to this article in the comments section below.

References:

[1]  http://www.math.montana.edu/jobo/phdprep/documents/phd6.pdf 

[2]  https://libguides.unf.edu/c.php?g=177129&p=1163732

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Literature Review Introduction Sample

How to Write Literature Review Introduction Sample

Table of contents, literature review (lr) introduction: revelation of concept, sample text 1, conceptual framework, declaration on lr type, sample text 2, follow referencing style, in-text referencing for lr introduction, sample text 3.

Notes- Footnotes & Endnotes

Sample Text 4

• MLA Style (8th edition)

Sample Text 5

The Literature Review (LR) is an integral part of an in-depth research process, which involves critically scrutinized content attained from former research works and empirical reports. In a research paper , the LR is meant to address the identified issue and gain adequate knowledge to resolve it. However, since every research is unique in its way, soon the researcher discovers that the former research works are inadequate or limited in meeting the current research objectives. In this way, the LR brings forth the research gaps, which leads to further research process at the researcher’s end. 

It is important to note here that the Literature Review format may differ from one University to another. However, the process of analysis and declarations remain universal. For the formatting and the inclusion list always check the University module.

In this article, we will focus on understanding the relevance and content to be established in the Introduction part of the Literature Review.

On a standard basis, the structure of the Literature Review is meant to offer three sections – Introduction, Body, and the Conclusion. In the case of Introduction, the researcher must offer detailed information about the context and the intellectual narration about the topic. Historical contexts and the developmental process of the concern need to be summed up in this section. The researcher should declare the theories and the relevance of the theories to the research in a very comprehensive manner. While elaborating the relevance of the selected theories the key writers and philosophers should be introduced in the Introduction section of the LR. 

It is highly recommended that the researcher considers the inclusion of the Conceptual Framework in the LR Introduction. The objective behind the inclusion of the Conceptual Framework is to develop an in-depth thinking process and thereby understand the complexity of the identified issue of the research. This framework acts as a roadmap while constructing the Body and Conclusion or the Research Gaps. The conceptual framework as prescribed in Figure 1 should be considered while answering the specified questions one-by-one:

Figure 1: Map to Construct the Conceptual Framework

The Literature Review Introduction can vary as per the type of review process considered by the researcher. Following the selected topic and the availability of secondary sources the LR can be:

• A narrative or argumentative type,
• A systematic review type with either of meta-synthesis or meta-analysis approach, or
• A theoretical or integrative review type.

For all these types, it is necessary that the Literature Review Introduction makes clear declarations about the selection process and justify the selection of the type in the most intellectually logical manner.

If you select the narrative approach to review the collected literature, then mention it in the first few lines. You need to state that you will summarise the content of the selected literature and will derive the research gaps.

Alternatively, your literature review can be argumentative in approach. In this case, the Literature Review Introduction must declare the process of examining the biases and ways to identify the shortcomings of the selected literature.

In case, you select a systematic review of very narrowly selected literature; make sure that you identify the right process. Since systematic literature review can be shaped as meta-analysis or as meta-synthesis, the LR Introduction must clarify the approach. Mention how you follow statistical procedures to meet the meta-analysis approach and undergo a deductive process under quantitative methodology. For the meta-synthesis approach, give a clear idea about the non-statistical techniques under qualitative methodology.

For the theoretical approach of the literature review, introduce and establish the relevance of the selected theories in the LR Introduction. On the other hand, for the integrative review approach, generate the necessary framework about the process of leading the critiques.

The literature Review Introduction will not mention anything about the selected referencing style. The in-text citations will make it all clear. You must follow the right kind of in-text referencing style as per your selected subject and approach of your research.

In this article, we are offering three samples for a clear understanding. These exemplified referencing styles are:

• American Psychological Association (APA) referencing system,
• Chicago referencing or Chicago Manual of Style (CMOS), &
• Modern Languages Association (MLA) referencing system.

It is the presence of the references in the form of ‘parenthetical in-text citations, which determines the selected referencing style for the entire research work. Note that for subjects from Humanities, the common selection is of MLA style. Even in Humanities, if you are from dealing with History, Business Fine Arts, then you can consider the Chicago style of referencing. As for the APA referencing style the subjects from Social Sciences, Engineering, Education, etc. remains as the basic selection.  Still, we would recommend that always have a consultation with your Guide or Supervisor about the right selection of the referencing style.

APA Style (7 th edition)

APA style  of referencing under 7 th edition is a parenthetical way of declaring the references. The bracketed mode of references that you need to add to the Literature Review Introduction must comprise of –

• The Surname of the Author
• Publication Date
• Page number or numbers

For instance, in Sample Text 1 for a fictitious book, ‘Evaluation of Education System’ by Simon Hillary , published in 2019; the APA style in-text referencing should appear like- (Hillary, 2019, p. 84) or (Hillary, 2019, pp. 84-88). Note that ‘p.’ stands for a single page, whereas ‘pp.’ for consecutive multiple pages. The page or page numbers are used when you quote from a text directly. In case there is no direct quote, you can avoid using the page or page numbers. In some cases like old texts, it is recommended to use paragraph or couplet numbers.

This format is a general application that varies slightly in the case of multiple authors. Let’s add Walter as co-author for two authored books. The in-text citations under the APA system follow the following provisions of using the commas ‘,’: There is no difference while referring to in-text reference to any book, journal or web article, or internet sources.

• For a book with a single author: (Hillary, 2019, p. 84) or (Hillary, 2019, pp. 84-88)
• For a book with two authors: (Hillary and Walter, 2019, p. 84) or (Hillary and Walter, 2019, pp. 84-88)
• For a book with multiple authors: (Hillary et al., 2019, p. 84) or (Hillary et al., 2019, pp. 84-88)
• Journal Article (both Print & Electronic), single author: (Hillary, 2019, p. 84) or (Hillary, 2019, pp. 84-88)
• Journal Article (both Print & Electronic), two authors: (Hillary and Walter, 2019, p. 84) or (Hillary and Walter, 2019, pp. 84-88)
• Journal Article (both Print & Electronic), multiple authors: (Hillary et al., 2019, p. 84) or (Hillary et al., 2019, pp. 84-88)
• Web Articles or Internet Sources, single author: (Hillary, 2019, p. 84) or (Hillary, 2019, pp. 84-88)
• Web Articles or Internet Sources, two authors: (Hillary and Walter, 2019, p. 84) or (Hillary and Walter, 2019, pp. 84-88)
• Web Articles or Internet Sources, multiple authors: (Hillary et al., 2019, p. 84) or (Hillary et al., 2019, pp. 84-88)

For APA in-text citations always remember:

• To capitalise all the proper nouns, this will include the surname/s of the author or authors,
• To capitalise the first alphabet of every word of any title is included in the text. Here, the prepositions and articles can remain in small letters.
• Indent of ½ inch from left for every direct quote in the text.

Chicago Style (17 th edition)

Chicago referencing style (17 th edition) is used for documentations of –

• Author-date citations, &
• Notes and bibliography.

Though this style is very similar to the APA style of adding-

Yet the placement of the comma makes all the difference in the in-text citation process. Instead of putting the comma ‘,’ after the Surname of the Author, Chicago places it after the publication date and there is no space for ‘p.’ or ‘pp.’.

If we consider the same text ‘Evaluation of Education System’ by Simon Hillary, published in 2019 by Oxford Open Press in Oxford; the Chicago style in-text referencing should appear like- (Hillary 2019, 84) or (Hillary 2019, 84-88). Let’s add Walter as co-author for two authored books.

Author-date (in-text)

There is no difference while referring to in-text reference to any book, journal or web article, or internet sources.

• For a book with a single author: (Hillary 2019, 84) or (Hillary 2019, 84-88)
• For a book with two authors: (Hillary and Walter 2019, 84) or (Hillary and Walter 2019, 84-88)
• For a book with multiple authors: (Hillary et al 2019, 84) or (Hillary et al 2019, 84-88)
• Journal Article (both Print & Electronic), single author: (Hillary 2019, 84) or (Hillary 2019, 84-88)
• Journal Article (both Print & Electronic), two authors: (Hillary and Walter 2019, 84) or (Hillary and Walter 2019, 84-88)
• Journal Article (both Print & Electronic), multiple authors: (Hillary et al 2019, 84) or (Hillary et al 2019, 84-88)
• Web Articles or Internet Sources, single author: (Hillary 2019, 84) or (Hillary 2019, 84-88)
• Web Articles or Internet Sources, two authors: (Hillary and Walter 2019, 84) or (Hillary and Walter 2019, 84-88)
• Web Articles or Internet Sources, multiple authors: (Hillary et al 2019, 84) or (Hillary et al 2019, 84-88)

The usage of Chicago is more particular when it comes to the inclusion of footnote or endnote in a text. Here, if you need to add any footnote or endnote to the Literature Review Introduction, then follow the following rules:

• For book: Full name of the Author, Book title (Place of Publication: Publisher, Publication year) page number/s
• Simon Hillary, Evaluation of Education System (Oxford: Oxford Open Press, 2019), 84-88
• Following in-text mentions – Hillary, Evaluation of Education System, 84-88
• For Journal Article: Full name of the Author, “Article Title,” Journal Name, Journal Volume, Journal No., Journal Issue (Month, Year): page number/s. Add DOI for electronic Journal publication.
• Edmund Walter, “Education System and Global Policies.” Journal for Intellect, 26, no. 3 (Summer, 2019): 65. https://doi.org/16.2329/jfiunivbchro.26.3.0065.
• Following in-text mentions – Walter, “Education System and Global Policies,” 65.
• For Web Articles or Internet Sources- “Page Title,” Name of the Website, Date of Access (Month-date-year), URL.
• “About Education System,” Educationresearch, accessed July 13, 2021, http://www.wr.dn/en/about-referencing-style.
• Following in-text mentions – “About Education System.”

MLA Style (8 th edition)

MLA referencing style under 8 th edition is also a parenthetical way of declaring the references. The brackets in the in-text referencing process for the Introduction of your Literature Review must comprise of –

• The Surname of the Author, and
• Page number/s of the text or context.

Considering the same book, ‘Evaluation of Education System’ by Simon Hillary, published in 2019; the MLA style in-text referencing should appear like- (Hillary 84) or (Hillary 84-88). It is important that in the case of MLA the non-consecutive pages are just added by commas, as in- (Hillary 84, 26, 104). Let’s add Walter as co-author for two authored books. There is no difference while referring to in-text reference to any book, journal or web article, or internet sources. Note that there is no use of ‘p.’ or ‘pp.’ for page number/s and there is no space for commas ‘,’.

• For a book with a single author: (Hillary 84) or (Hillary 84-88)
• For a book with two authors: (Hillary and Walter 84) or (Hillary and Walter 84-88)
• For a book with multiple authors: (Hillary et al 84) or (Hillary et al 84-88)
• Journal Article (both Print & Electronic), single author: (Hillary 84) or (Hillary 84-88)
• Journal Article (both Print & Electronic), two authors: (Hillary and Walter 84) or (Hillary and Walter 84-88)
• Journal Article (both Print & Electronic), multiple authors: (Hillary et al 84) or (Hillary et al 84-88)
• Web Articles or Internet Sources, single author: (Hillary 84) or (Hillary 84-88)
• Web Articles or Internet Sources, two authors: (Hillary and Walter 84) or (Hillary and Walter 84-88)
• Web Articles or Internet Sources, multiple authors: (Hillary et al 84) or (Hillary et al 84-88)

The MLA style is popular for its facilities to accommodate various kinds of exceptional in-text citations. In your Literature Review Introduction, these exceptions can occur in the following manner, yet MLA holds solutions for the-

No Author Citation: The in-text citation needs to be added by matching the very foremost element in the entry of the Cited Work, which can be the organisation’s name or source title.

Example: For the source- United Nations International Children's Emergency Fund. International Annual Report for FY 2020-21, the in-text citation would be UNICEF (or United Nations International Children's Emergency Fund) 162.

No Page Number/s Citation: In an in-text citation, when there is no page number, then you can consider the number of the chapter, scene, section, or anything that can locate the page.

Example: For the source- ‘Evaluation of Education System’ by Simon Hillary, the in-text citation would be (Hillary ch 2).

Same Author Different Sources:   The in-text citation of different works by the same author, MLA follows the regulation of shortening the title of the sources.

Example: For the source- ‘Evaluation of Education System’ by Simon Hillary, and ‘Education in Global Platform’ by Simon Hillary, the in-text citation would be (Hillary, Evaluation 84; and Hilary, Global 65).

Same Last Names: The in-text citation of different authors with the same surnames, MLA follows the trend of adding the First name initial.

Example: For the authors- Thomas Hilary and Simon Hilary with different sources, the in-text citation would be (T. Hillary 65 & S. Hillary 84).

Indirect Citation: The in-text citation for the information attained from indirect sources, MLA prescribes the provision of adding the source with parentheses and by the end of the sentence.

Example: If a piece of information about Hillary has been gathered from James Walter’s text published in 2020, then the in-text citation would be Hillary declared that the style of referencing … (Walter ch.2)

MLA style is very peculiar for its art of paraphrasing or delivering the context with the sources. For instance, in your Introduction, you can have sentences like-

In the conclusion, it is suggested that the Literature Review Introduction is very important for the success of your research However, to get your research approved by the University you need to take care of all the aspects and points mentioned above. 

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• Volume 24, Issue 2
• Five tips for developing useful literature summary tables for writing review articles
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• http://orcid.org/0000-0003-0157-5319 Ahtisham Younas 1 , 2 ,
• http://orcid.org/0000-0002-7839-8130 Parveen Ali 3 , 4
• 1 Memorial University of Newfoundland , St John's , Newfoundland , Canada
• 2 Swat College of Nursing , Pakistan
• 3 School of Nursing and Midwifery , University of Sheffield , Sheffield , South Yorkshire , UK
• 4 Sheffield University Interpersonal Violence Research Group , Sheffield University , Sheffield , UK
• Correspondence to Ahtisham Younas, Memorial University of Newfoundland, St John's, NL A1C 5C4, Canada; ay6133{at}mun.ca

https://doi.org/10.1136/ebnurs-2021-103417

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Introduction

Literature reviews offer a critical synthesis of empirical and theoretical literature to assess the strength of evidence, develop guidelines for practice and policymaking, and identify areas for future research. 1 It is often essential and usually the first task in any research endeavour, particularly in masters or doctoral level education. For effective data extraction and rigorous synthesis in reviews, the use of literature summary tables is of utmost importance. A literature summary table provides a synopsis of an included article. It succinctly presents its purpose, methods, findings and other relevant information pertinent to the review. The aim of developing these literature summary tables is to provide the reader with the information at one glance. Since there are multiple types of reviews (eg, systematic, integrative, scoping, critical and mixed methods) with distinct purposes and techniques, 2 there could be various approaches for developing literature summary tables making it a complex task specialty for the novice researchers or reviewers. Here, we offer five tips for authors of the review articles, relevant to all types of reviews, for creating useful and relevant literature summary tables. We also provide examples from our published reviews to illustrate how useful literature summary tables can be developed and what sort of information should be provided.

Tip 1: provide detailed information about frameworks and methods

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Tabular literature summaries from a scoping review. Source: Rasheed et al . 3

The provision of information about conceptual and theoretical frameworks and methods is useful for several reasons. First, in quantitative (reviews synthesising the results of quantitative studies) and mixed reviews (reviews synthesising the results of both qualitative and quantitative studies to address a mixed review question), it allows the readers to assess the congruence of the core findings and methods with the adapted framework and tested assumptions. In qualitative reviews (reviews synthesising results of qualitative studies), this information is beneficial for readers to recognise the underlying philosophical and paradigmatic stance of the authors of the included articles. For example, imagine the authors of an article, included in a review, used phenomenological inquiry for their research. In that case, the review authors and the readers of the review need to know what kind of (transcendental or hermeneutic) philosophical stance guided the inquiry. Review authors should, therefore, include the philosophical stance in their literature summary for the particular article. Second, information about frameworks and methods enables review authors and readers to judge the quality of the research, which allows for discerning the strengths and limitations of the article. For example, if authors of an included article intended to develop a new scale and test its psychometric properties. To achieve this aim, they used a convenience sample of 150 participants and performed exploratory (EFA) and confirmatory factor analysis (CFA) on the same sample. Such an approach would indicate a flawed methodology because EFA and CFA should not be conducted on the same sample. The review authors must include this information in their summary table. Omitting this information from a summary could lead to the inclusion of a flawed article in the review, thereby jeopardising the review’s rigour.

Tip 2: include strengths and limitations for each article

Critical appraisal of individual articles included in a review is crucial for increasing the rigour of the review. Despite using various templates for critical appraisal, authors often do not provide detailed information about each reviewed article’s strengths and limitations. Merely noting the quality score based on standardised critical appraisal templates is not adequate because the readers should be able to identify the reasons for assigning a weak or moderate rating. Many recent critical appraisal checklists (eg, Mixed Methods Appraisal Tool) discourage review authors from assigning a quality score and recommend noting the main strengths and limitations of included studies. It is also vital that methodological and conceptual limitations and strengths of the articles included in the review are provided because not all review articles include empirical research papers. Rather some review synthesises the theoretical aspects of articles. Providing information about conceptual limitations is also important for readers to judge the quality of foundations of the research. For example, if you included a mixed-methods study in the review, reporting the methodological and conceptual limitations about ‘integration’ is critical for evaluating the study’s strength. Suppose the authors only collected qualitative and quantitative data and did not state the intent and timing of integration. In that case, the strength of the study is weak. Integration only occurred at the levels of data collection. However, integration may not have occurred at the analysis, interpretation and reporting levels.

Tip 3: write conceptual contribution of each reviewed article

While reading and evaluating review papers, we have observed that many review authors only provide core results of the article included in a review and do not explain the conceptual contribution offered by the included article. We refer to conceptual contribution as a description of how the article’s key results contribute towards the development of potential codes, themes or subthemes, or emerging patterns that are reported as the review findings. For example, the authors of a review article noted that one of the research articles included in their review demonstrated the usefulness of case studies and reflective logs as strategies for fostering compassion in nursing students. The conceptual contribution of this research article could be that experiential learning is one way to teach compassion to nursing students, as supported by case studies and reflective logs. This conceptual contribution of the article should be mentioned in the literature summary table. Delineating each reviewed article’s conceptual contribution is particularly beneficial in qualitative reviews, mixed-methods reviews, and critical reviews that often focus on developing models and describing or explaining various phenomena. Figure 2 offers an example of a literature summary table. 4

Tabular literature summaries from a critical review. Source: Younas and Maddigan. 4

Tip 4: compose potential themes from each article during summary writing

While developing literature summary tables, many authors use themes or subthemes reported in the given articles as the key results of their own review. Such an approach prevents the review authors from understanding the article’s conceptual contribution, developing rigorous synthesis and drawing reasonable interpretations of results from an individual article. Ultimately, it affects the generation of novel review findings. For example, one of the articles about women’s healthcare-seeking behaviours in developing countries reported a theme ‘social-cultural determinants of health as precursors of delays’. Instead of using this theme as one of the review findings, the reviewers should read and interpret beyond the given description in an article, compare and contrast themes, findings from one article with findings and themes from another article to find similarities and differences and to understand and explain bigger picture for their readers. Therefore, while developing literature summary tables, think twice before using the predeveloped themes. Including your themes in the summary tables (see figure 1 ) demonstrates to the readers that a robust method of data extraction and synthesis has been followed.

Tip 5: create your personalised template for literature summaries

Often templates are available for data extraction and development of literature summary tables. The available templates may be in the form of a table, chart or a structured framework that extracts some essential information about every article. The commonly used information may include authors, purpose, methods, key results and quality scores. While extracting all relevant information is important, such templates should be tailored to meet the needs of the individuals’ review. For example, for a review about the effectiveness of healthcare interventions, a literature summary table must include information about the intervention, its type, content timing, duration, setting, effectiveness, negative consequences, and receivers and implementers’ experiences of its usage. Similarly, literature summary tables for articles included in a meta-synthesis must include information about the participants’ characteristics, research context and conceptual contribution of each reviewed article so as to help the reader make an informed decision about the usefulness or lack of usefulness of the individual article in the review and the whole review.

In conclusion, narrative or systematic reviews are almost always conducted as a part of any educational project (thesis or dissertation) or academic or clinical research. Literature reviews are the foundation of research on a given topic. Robust and high-quality reviews play an instrumental role in guiding research, practice and policymaking. However, the quality of reviews is also contingent on rigorous data extraction and synthesis, which require developing literature summaries. We have outlined five tips that could enhance the quality of the data extraction and synthesis process by developing useful literature summaries.

• Aromataris E ,
• Rasheed SP ,

Twitter @Ahtisham04, @parveenazamali

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient consent for publication Not required.

Provenance and peer review Not commissioned; externally peer reviewed.

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• Volume 14, Issue 4
• Comparison of the efficacy and tolerability of different repetitive transcranial magnetic stimulation modalities for post-stroke dysphagia: a systematic review and Bayesian network meta-analysis protocol
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• http://orcid.org/0009-0001-2981-9322 Qiang Chen 1 ,
• http://orcid.org/0009-0005-3248-0875 Mengfan Kan 1 ,
• http://orcid.org/0000-0002-8404-5032 Xiaoyu Jiang 1 ,
• http://orcid.org/0000-0003-3918-3775 Huifen Liu 1 ,
• Deqi Zhang 1 ,
• Lin Yuan 1 ,
• Qiling Xu 1 ,
• Hongyan Bi 2
• 1 College of Rehabilitation Medicine , Shandong University of Traditional Chinese Medicine , Jinan , Shandong , China
• 2 Department of Rehabilitation Medicine , Shandong University of Traditional Chinese Medicine Affiliated Hospital , Jinan , Shandong , China
• Correspondence to Professor Hongyan Bi; Hy__bi{at}163.com

Introduction Up to 78% of patients who had a stroke develop post-stroke dysphagia (PSD), a significant consequence. Life-threatening aspiration pneumonia, starvation, and water and electrolyte abnormalities can result. Several meta-analyses have shown that repeated transcranial magnetic stimulation (rTMS) improves swallowing in patients who had a stroke; however, the optimum model is unknown. This study will be the first Bayesian network meta-analysis (NMA) to determine the best rTMS modalities for swallowing of patients who had a stroke.

Methods and analysis PubMed, Web of Science, Embase, Google Scholar, Cochrane, the Chinese National Knowledge Infrastructure, the Chongqing VIP Database and WanFang Data will be searched from their creation to 2 September 2023. All randomised controlled trials associated with rTMS for PSD will be included. Only Chinese or English results will be studied. Two researchers will independently review the literature and extract data, then use the Cochrane Collaboration’s Risk of Bias 2.0 tool to assess the included studies’ methodological quality. The primary outcome is swallowing function improvement, whereas secondary outcomes include side effects (eg, paraesthesia, vertigo, seizures) and quality of life. A pairwise meta-analysis and NMA based on a Bayesian framework will be conducted using Stata and R statistical software. The Grading of Recommendations Assessment, Development, and Evaluation system will assess outcome indicator evidence quality.

Ethics and dissemination As all data in this study will be taken from the literature, ethical approval is not needed. We will publish our work in peer-reviewed publications and present it at academic conferences.

PROSPERO registration number CRD42023456386.

• Transcranial Magnetic Stimulation
• Systematic Review
• REHABILITATION MEDICINE

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:  http://creativecommons.org/licenses/by-nc/4.0/ .

https://doi.org/10.1136/bmjopen-2023-080289

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STRENGTHS AND LIMITATIONS OF THIS STUDY

This study will collect a wide range of evidence to assess the efficacy and tolerability of repetitive transcranial magnetic stimulation for post-stroke dysphagia.

The study’s outcome indicators will be coupled with the subjective assessment scale and objective physiological index.

The Grading of Recommendations Assessment, Development, and Evaluation system will be implemented to assess the quality of the evidence.

Language bias may result from searching solely Chinese and English databases for literature.

Introduction

Stroke is the second leading cause of death and the third leading cause of disability worldwide, 1 2 with more than 17 million new cases reported each year. 3 The Global Burden of Disease Study 2019 showed that about 101 million people have a stroke worldwide, and the number of deaths due to stroke has reached 65.5 million. 4 Sequelae of varying degrees can occur after stroke, such as dyskinesia, cognitive impairment, dysphagia, speech disorder, anxiety, depression, fatigue and other symptoms, which cause a heavy burden on the lives of patients and their families. 5–8 Among them, post-stroke dysphagia (PSD) is a common and serious complication after stroke, and its incidence ranges from 37% to 78%. 6 About 20–43% of patients have persistent dysphagia after 3 months, mainly manifested as choking on drinking, unable to eat and can cause a variety of complications, such as aspiration pneumonia, malnutrition, and water and electrolyte disorders. 9 In severe cases, it may lead to asphyxia, thereby increasing the risk of death. 10 In addition, PSD can further lead to a series of psychological problems in patients, such as fear of eating, anxiety, depression, among others, which cause serious distress to patients’ psychology and daily lives. 11 12 However, these negative psychological states will in turn lead to the aggravation of PSD, which affects the recovery and quality of life of patients, thus forming a vicious circle. 13 14 It is worth noting that early screening, intervention and management of PSD have not received enough attention. 15 16 Consequently, the timely diagnosis and effective treatment of PSD have become urgent problems to be solved in clinical work.

The pathogenesis of PSD is quite complex, which may be related to damage to the swallowing cortical centre, descending cortical fibres, bulbar swallowing centre and extrapyramidal system. 17–20 At present, the clinical treatment methods for PSD are limited. Compensatory interventions based on diet and nutrition interventions combined with recovery interventions based on swallowing function rehabilitation training are widely used. 21 22 However, these therapies have problems such as inflated cost, long cycle and poor compliance, which are not conducive to clinical application. 23–25 Nevertheless, repetitive transcranial magnetic stimulation (rTMS), as a non-invasive treatment technique, can directly regulate the excitability of the swallowing cortex or promote the reorganisation of swallowing cortex function by generating evoked potentials through pulsed magnetic fields. It has the advantages of simple operation, being non-invasive, painless and having high safety, and it does not require the active cooperation of patients, which brings new opportunities for the treatment of PSD. 24 25

There are various stimulation modalities for treating PSD with rTMS. It is believed that low-frequency rTMS (LF-rTMS) (≤1 Hz) can attenuate cortical excitability, while high-frequency rTMS (HF-rTMS) (>1 Hz) can enhance cortical excitability. 26 27 Consequently, previous studies usually used HF-rTMS (3 Hz, 5 Hz and 10 Hz) to stimulate (excite) the lesion side (the affected side) or LF-rTMS (1 Hz) to stimulate (inhibit) the non-lesion side (the healthy side) to improve the swallowing function of patients with PSD. 28–30 The selection of the above stimulation modality is dependent on the competitive cerebral hemisphere model. rTMS can enhance or inhibit the excitability of the contralateral cerebral hemisphere, reshape the balance between the two hemispheres and thus achieve the goal of restoring swallowing function after stroke. 31 32 In addition, some studies have shown that HF-rTMS of the contralateral cerebral cortex or bilateral cerebral cortex stimulation can also improve or even contribute to the recovery of swallowing function in patients with PSD. Some researchers have also shown that HF-rTMS of the opposite cerebral cortex or stimulation of both cerebral cortices can help patients with PSD swallow better or even get their swallowing back. 24 33–37 This may be related to functional reorganisation and compensation of the swallowing motor cortex function in the contralateral hemisphere. 38 39 As a result, there are significant debates about whether rTMS should be applied to the affected side, the healthy side or both sides, and whether LF-rTMS or HF-rTMS should be applied on this basis.

At present, many scholars have conducted evidence-based medical research on rTMS in the PSD. 40–42 Liao et al published a systematic review and meta-analysis in 2017, which confirmed that rTMS has a positive effect on PSD. Moreover, compared with LF-rTMS, HF-rTMS may be more beneficial to patients. 40 Tan et al also conducted a systematic review and meta-analysis in 2022 and found that rTMS has a long-term effect on the recovery of swallowing function after stroke. 41 Hsiao et al published a meta-analysis in 2023, which confirmed that both HF-rTMS on the affected side and LF-rTMS on the healthy side could improve the swallowing function of patients who had a stroke. 42 However, they are based on traditional meta-analysis methods, which can only achieve a direct comparison between two interventions and lack a comparison of the efficacy of different rTMS modalities. Network meta-analysis (NMA) can be used to compare the efficacy of different rTMS treatment regimens.

Consequently, this study will use the Bayesian NMA method to compare the efficacy of different rTMS modalities, rank their effectiveness and synthesise the results to obtain the best rTMS treatment regimens and provide reliable and comprehensive evidence for clinical treatment decisions in patients with PSD.

Methods and analyses

Protocol design and registration.

We plan to do a systematic review and NMA based on a Bayesian framework. This protocol was implemented according to the Preferred Reporting Item for Systematic Reviews and Meta-Analyses Protocol 43 and has been registered on PROSPERO (CRD42023456386). Any amendments to this agreement will be made through PROSPERO.

Inclusion criteria

Types of studies.

Only randomised controlled trials (RCTs) presented in English or Chinese will be included in the study. Animal trials, meta-analyses, systematic reviews, abstracts, conference presentations, case reports and cohort studies will be excluded.

Types of participants

All participants will meet the following criteria: (1) patients with ischaemic or haemorrhagic stroke (including cerebral hemisphere and brain stem) diagnosed by CT, MRI and other related examinations, not limited to stroke stage; (2) patients with a final diagnosis of swallowing dysfunction on a clinical swallowing-related scale or by objective instrumental examination; and (3) adult patients (≥18 years old) regardless of gender, ethnicity, race and education level.

Types of interventions

The intervention of the experimental group may be rTMS treatment with different stimulation modalities. Based on our previous literature search, rTMS treatment regimens may have a choice of five stimulation modalities. Among the stimulation modalities will mainly include LF-rTMS on the healthy side, 27 30 HF-rTMS on the affected side, 24 30 32 34 36 37 HF-rTMS on the healthy side, 32 33 35–37 HF-rTMS bilaterally 24 32 34 36 37 and LF-rTMS on the healthy side combined with HF-rTMS on the affected side. 44

Types of control groups

The control group may be conventional rehabilitation therapy, sham stimulation therapy or another rTMS treatment regimen different from the experimental group.

The primary outcome will be improvement in swallowing function, which will be measured with a swallowing assessment scale and objective physiological measures of swallowing function. Among them, the Standardized Swallowing Assessment (SSA) and the Penetration Aspiration Scale (PAS) will be included in the subjective swallowing assessment. Objective swallowing measurements will include a videofluoroscopic swallowing study (VFSS) and surface electromyography (sEMG). The secondary outcomes will include quality-of-life measures such as the Swallowing Quality-of-Life Questionnaire and adverse events (including dizziness, headache, paraesthesia, seizures). The tolerability of the rTMS intervention will be evaluated by the occurrence of adverse events.

PAS is an indicator of food invasion into the airways. The score is between 1 and 8 points, with a higher score indicating a higher risk of aspiration and a greater degree of dysphagia. 45 The SSA is composed of three parts 46 : (1) the clinical examination mainly includes eight items such as consciousness level, head and trunk control, and lip control, with a total score of 8–23 points; (2) the patient is asked to swallow 5 mL of water three times, and the mouth is observed for running water, laryngeal movement, repeated swallowing, wheezing during swallowing and laryngeal function after swallowing, with a total score of 5–11 points; (3) if no abnormal manifestations are observed in the above examination, the patient is instructed to drink 60 mL of water. Observations are made to check whether the patient can consume all the water, if there is any coughing or wheezing during or after swallowing, if there is any laryngeal function impairment after swallowing and if there is any sign of aspiration. The total score is 5–12 points. The SSA scores range from 18 to 46, with higher scores indicating more severe dysphagia in the patient. sEMG can quantitatively evaluate the functional status of neuromusculars during swallowing, reflect the difficulty and duration of tongue–laryngeal complex elevation and predict the risk of aspiration in patients with dysphagia. 47 VFSS can evaluate the situation throughout the swallowing stage, dynamically observe the delivery of food and diagnose whether there is a hidden aspiration, which is recognised as the gold standard for the diagnosis of dysphagia. 48

Exclusion criteria

We will refer to the following exclusion criteria: (1) non-RCTs, including cohort studies, case reports, meta-analyses, reviews and conference papers; (2) dysphagia not caused by stroke (eg, trauma, Parkinson’s disease); (3) outcome indicators related to swallowing function were not reported; (4) repeated publication; and (5) full text cannot be obtained or data cannot be extracted.

Data sources and search strategy

We will search PubMed, Web of Science, Embase, Google Scholar, Cochrane, China National Knowledge Infrastructure, Chongqing VIP Database and WanFang Data from the database’s inception to 2 September 2023. All RCTs related to rTMS for PSD will be included. The studies will be limited to results published in Chinese or English. The search terms will include “repetitive transcranial magnetic stimulation”, “rTMS”, “post-stroke dysphagia”, “PSD” and other related terms. At the same time, we will conduct a secondary manual search of the references in the included literature and relevant systematic reviews to avoid missing important literature. In the case of PubMed, we will present the search strategy in detail in the online supplemental material .

Supplemental material

Study selection.

First, two researchers (LY and DZ) will use EndNote V.X9 software to eliminate duplicate literature, then they will conduct a preliminary screen of the literature by reading the title and abstract to exclude the articles that do not meet the inclusion criteria, and finally, they will evaluate the potentially qualified studies by reading the full text to determine the final included literature. In case of any disagreement, the third researcher (QX) will help to resolve the problem. We will present the entire literature screening process in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow chart, 43 and the detailed process is shown in figure 1 .

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Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow chart of study selection.

Data extraction

After two researchers (LY and DZ) read the final included literature, the following data will be extracted separately: (1) basic information (first author, publication time, country, sample size, intervention measures); (2) patient information (mean age, gender, hemiplegic side of stroke, stroke stage, course of disease); (3) rTMS-specific parameters and treatment protocols (stimulation frequency, stimulation target, stimulation intensity, total number of pulses, coil type, treatment protocol and duration); and (4) outcome measures (data on each outcome and adverse event and follow-up time). In cases of disagreement, the third researcher (QX) will assist in resolution.

Risk-of-bias assessment

Two researchers (LY and DZ) will independently evaluate the literature that meets the inclusion criteria using the Risk of Bias 2.0 provided by Cochrane Collaboration. 49 It consists of the following five aspects: (1) bias in the randomisation process; (2) bias from the intended intervention; (3) bias of missing outcome data; (4) outcome measurement bias and (5) bias of selective reporting. The degree of risk of bias was divided into ‘low risk of bias’, ‘high risk of bias’ and ‘uncertain risk of bias’. The overall risk of bias in a study was determined by combining the level of bias for each item. In cases of disagreement, the third researcher (QX) will participate and reach a consensus.

Data synthesis and statistical analyses

Pairwise meta-analysis.

Before performing the NMA, we will perform a standard pairwise meta-analysis using Stata V.14.2 (StataCorp, College Station, Texas, USA). Χ 2 test and I 2 statistic will be used to evaluate the heterogeneity of the studies. If I 2 ≤50%, indicating less heterogeneity, the fixed-effects model will be used for pooling. If I 2 >50%, indicating large heterogeneity, the random-effects model will be selected for pooling. 50 For continuous variables, the mean difference (MD) and its 95% CI will be used if the measurement instrument is the same. The standard MD and its 95% CI will be used if the measurement instrument is different. For dichotomous data, relative risk and its 95% CI will be used.

Network meta-analysis

We will perform a Bayesian NMA using Stata V.14.2 and R (V.4.1.2) (available at Index of/src/base/R-4 ( r-project.org )). Stata V.14.2 will be used to draw a network plot for different stimulation modalities of rTMS. In addition, the efficacy of different rTMS modalities will be ranked according to the surface under the cumulative ranking curve provided by Stata V.14.2. We will use R (V.4.1.2) to perform Bayesian NMA of random-effects models and use the Markov Chain Monte Carlo algorithm for statistical calculation. Each model will use four Markov chains to set the initial values. The number of iterations will be 50 000: the first 20 000 will be used for annealing to eliminate the influence of the initial values and the last 30 000 will be used for sampling calculations. 51 52

Assessment of similarity and consistency

Based on the selection of the above effect indicators, the principle of framework construction and the selection of statistical methods, R (V.4.1.0) software will be used to construct the consistency model and inconsistency model of Bayesian NMA and calculate their relevant results. R (V.4.1.0) software will be used to build the consistency model and the inconsistency model of Bayesian NMA and figure out their results. This is based on the choice of the above effect indicators, the framework construction principle and the statistical methods. 52 For the Bayesian NMA results of the generated consistency model and inconsistency model, we will use the Deviance Information Criterion (DIC) for global inconsistency detection. Significant global inconsistencies will be considered if the difference in DIC values between the two models is greater than one. For local inconsistency tests, if the outcome forms a closed-loop structure (including any pairwise direct comparisons), we will use node splitting to detect inconsistencies between direct and indirect comparisons. If there are any pairwise direct comparisons in the outcome of a local inconsistency test, we will use node splitting to find problems between direct and indirect comparisons if the structure is closed. Local inconsistency in the results will be considered at p<0.05; if the network diagram does not form a closed-loop structure, the inconsistency between the two results above will be determined directly by visual inspection. For the trace and density map and convergence diagnostics map generated by R (V.4.1.0), convergence diagnosis will be carried out through the Brooks-Gelman-Rubin method. If the potential scale reduced factor value is close to 1, it can be considered that the convergence is good, which will indicate that the statistical results are stable and credible.

Sensitivity analysis and subgroup analysis

When heterogeneity is significant, we will carefully read the original literature again to find whether there are significant clinical, methodological and statistical differences between studies. 53 We will further explore sources of heterogeneity by performing sensitivity analyses or subgroup analyses with the use of Stata V.14.2. 54

Meta-regression analysis

If necessary, we will perform a meta-regression analysis of factors such as patient demographics that may contribute to heterogeneity between studies. If the meta-regression coefficient is p<0.05, it will be considered one of the sources of heterogeneity. 55

Assessment of publication bias

If the number of included studies exceeds 10, we will assess small-study effects or the publication bias by the comparison-adjusted funnel plots generated and the results of Egger’s test. 56 57

Quality of evidence

The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) will be applied to evaluate the quality of evidence for all outcomes in the pairwise and network meta-analyses. Two researchers will import the data into GRADEprofiler software (GRADEpro, V.3.6.1) (available at www.gradeworkinggroup.org ), respectively, to evaluate the quality of the evidence. The GRADE system will include five evaluation items: risk of bias, inconsistency, indirectness, precision and publication bias. 58 The level of evidence was graded as very low, low, moderate and high. 59

Patient and public involvement

There will be no direct patient or public involvement in any aspect of this study.

Ethics and dissemination

As a literature-based systematic review and NMA, the data used in this study will all be extracted from pre-existing literature. Therefore, ethical approval is not required for this study. The findings will be submitted to peer-reviewed journals and disseminated at national/international academic conferences.

In recent years, with the development of brain imaging technology and non-invasive nerve stimulation technology, as well as the understanding of the neurophysiological characteristics of swallowing, rTMS has become one of the methods for the treatment of PSD. Many studies have confirmed the effectiveness of rTMS in the treatment of dysphagia and its superiority over other techniques. 42 60 61 The guideline for the diagnosis and treatment of PSD published by the European Stroke Organisation and European Society also recommends rTMS for PSD and suggests that it is more beneficial in combination with conventional swallowing therapy. 62 However, there is no unified standard for the selection of stimulation modalities when rTMS is used to treat PSD. In addition, there is no clear evidence-based medical evidence to support which stimulation modalities has the best effect. To some extent, these will lead to controversy and confusion in clinical application and hinder the process of recovery of patients with dysphagia after stroke.

This study conducted a comprehensive and quantitative analysis of the published literature data by the method of NMA to explore the effectiveness of different rTMS modalities, and to provide a basis for the comprehensive prevention and treatment of stroke dysphagia. Nonetheless, the study has several limitations: First, the severity, stage and lesion location of patients who had a stroke in this study were not uniform, and the effect of heterogeneity cannot be fully excluded. Second, the languages of the included articles were limited to Chinese and English, which may leave out valuable literature. Finally, the ranking of results based on NMA is only a statistical and methodological reference, due to the method itself still having some defects and limitations of application, the choice of rTMS should still be used in conjunction with the specific conditions of patients in the clinical process.

To the best of our knowledge, the present study will be the first systematic review and Bayesian NMA to compare the efficacy and tolerability of different rTMS modalities for PSD. The results of this study will help physicians and patients choose the optimal rTMS treatment and provide the latest theoretical basis for the rehabilitation application of rTMS in PSD.

Ethics statements

Patient consent for publication.

Not applicable.

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Contributors QC conceived the original idea and initiated this protocol. HB was responsible for quality control and review of the articles. LY, DZ and QX participated in literature screening and literature extraction. The manuscript was prepared and written by QC and MK. XJ and LY collaborated on the revision of the paper. HL and MK conducted data analysis. All authors read and agreed to publish the protocol.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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• Published: 21 June 2022

Fluid challenge in critically ill patients receiving haemodynamic monitoring: a systematic review and comparison of two decades

• Antonio Messina 1 , 2 ,
• Lorenzo Calabrò 1 ,
• Luca Pugliese 1 ,
• Aulona Lulja 1 ,
• Alexandra Sopuch 1 ,
• Daniela Rosalba 3 ,
• Emanuela Morenghi 1 , 2 ,
• Glenn Hernandez 4 ,
• Xavier Monnet 5 , 6 , 7 &
• Maurizio Cecconi 1 , 2  

Critical Care volume  26 , Article number:  186 ( 2022 ) Cite this article

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Introduction

Fluid challenges are widely adopted in critically ill patients to reverse haemodynamic instability. We reviewed the literature to appraise fluid challenge characteristics in intensive care unit (ICU) patients receiving haemodynamic monitoring and considered two decades: 2000–2010 and 2011–2021.

We assessed research studies and collected data regarding study setting, patient population, fluid challenge characteristics, and monitoring. MEDLINE, Embase, and Cochrane search engines were used. A fluid challenge was defined as an infusion of a definite quantity of fluid (expressed as a volume in mL or ml/kg) in a fixed time (expressed in minutes), whose outcome was defined as a change in predefined haemodynamic variables above a predetermined threshold.

We included 124 studies, 32 (25.8%) published in 2000–2010 and 92 (74.2%) in 2011–2021, overall enrolling 6,086 patients, who presented sepsis/septic shock in 50.6% of cases. The fluid challenge usually consisted of 500 mL (76.6%) of crystalloids (56.6%) infused with a rate of 25 mL/min. Fluid responsiveness was usually defined by a cardiac output/index (CO/CI) increase ≥ 15% (70.9%). The infusion time was quicker (15 min vs 30 min), and crystalloids were more frequent in the 2011–2021 compared to the 2000–2010 period.

Conclusions

In the literature, fluid challenges are usually performed by infusing 500 mL of crystalloids bolus in less than 20 min. A positive fluid challenge response, reported in 52% of ICU patients, is generally defined by a CO/CI increase ≥ 15%. Compared to the 2000–2010 decade, in 2011–2021 the infusion time of the fluid challenge was shorter, and crystalloids were more frequently used.

Fluid administration in the intensive care unit (ICU) is one of the most common and disputed interventions triggered at the bedside by several clinical variables [ 1 , 2 ].

Fluid therapy aims to increase stroke volume (SV) and cardiac output (CO) to optimise systemic blood flow and tissue perfusion. As with any therapeutic intervention, the final clinical effect elicited may vary because of a complex interplay between the patient's intrinsic conditions and the therapy itself.

Fluid responsiveness can occur only if both ventricles work on the ascending, steep part of the Frank–Starling curve, i.e. in cases where CO is preload dependent [ 3 , 4 ]. Preload dependency is assessed using a diagnostic test performed by infusing a fixed aliquot of fluid, the fluid challenge [ 5 , 6 , 7 ]. From a clinical perspective, this approach also allows titration of fluid administration (when the patient becomes no longer responsive to the fluid challenge) and reduces the risk of fluid overload, which worsens the outcome of ICU patients [ 8 , 9 ].

Several variables defining the characteristics of the fluid challenge have been further investigated in studies adopting continuous haemodynamic monitoring, showing that the amount of fluids given, the rate of administration, and the threshold adopted to define fluid responsiveness impact the outcome of a fluid challenge [ 10 , 11 , 12 ]. Moreover, despite conflicting results on shock reversal efficacy between crystalloids and colloids, crystalloids are now recommended as the first-line fluid type in patients with septic shock, being inexpensive and widely available. Also, the administration of colloids compared to crystalloids has not demonstrated any clear benefit in the literature [ 13 , 14 ].

However, neither the nature, mode of administration, and method to assess the effectiveness of the fluid challenge are standardised in current clinical practice, and the definition of fluid challenge responsiveness is also variable among studies [ 15 , 16 , 17 , 18 ].

Whether or not these findings have modified the modalities of fluid challenge and the definition of fluid responsiveness in published studies is uncertain. To address this issue, we systematically reviewed existing literature from the year 2000. We appraised the characteristics of fluid challenges in critically ill patients (i.e., amount and kind of fluid administration, time of infusion, hemodynamic variables, and thresholds for fluid responsiveness) enrolled in research studies receiving continuous haemodynamic monitoring and assessed the relationship between the reported fluid responsiveness and predefined independent variables. Secondarily, we compared data from studies published in 2011–2021 versus those published in 2000–2010.

Material and methods

We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis-Protocols (PRISMA-P) guidelines (Additional file 1 : Table S1). The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) in November 2021 (CRD42021284761).

Search strategy

A systematic literature search was performed, including the following databases: PUBMED®, EMBASE®, and the Cochrane Controlled Clinical trials register. The following keywords and their related MeSh terms were used: “fluid challenge”, “fluid responsiveness”, “stroke volume variation”, “pulse pressure variation”, “dynamic indices OR indexes”, “passive leg raising”, OR “passive leg raising test”, “functional haemodynamic test OR tests”. Included papers were also examined to identify other studies of interest missed during the primary search.

Study selection and inclusion criteria

Articles enrolling at least 20 adult critically ill patients, written in English and published from 1st January 2000 to 31st December 2021 in indexed scientific journals, were considered. Editorials, commentaries, letters to the editor, opinion articles, reviews, and meeting abstracts were excluded. Studies enrolling paediatric or obstetric populations were excluded. References of selected papers, review articles, commentaries, and editorials on this topic were also reviewed to identify other studies of interest missed during the primary search. When multiple publications of the same research group/centre described potentially overlapping cohorts, the most recent publications were selected.

A fluid challenge was defined as an infusion of a definite quantity of fluid (expressed as a volume in mL or ml/kg) in a fixed time (expressed in minutes), whose outcome was defined as a change in one of the following haemodynamic variables above a predetermined threshold: CO, cardiac index (CI), SV, SV index (SVI), or surrogate of SV, i.e., velocity–time integral (VTI) in the left ventricular outflow tract and aortic blood flow (ABF), as assessed by transthoracic, transoesophageal echocardiography or oesophageal Doppler. We included studies adopting both a specific (i.e., Ringer lactate, saline, etc.) and a broad definition (i.e., crystalloids, colloids, etc.) of the fluid used for the fluid challenge. Studies adopting changes in systemic arterial pressure to define fluid responsiveness were excluded. Finally, we considered the predefined clinical reasons and triggers to start fluid challenge infusion.

Data extraction

Three couples of examiners independently evaluated titles and abstracts. The articles were then subdivided into three subgroups: “included” and “excluded” (if the two examiners agreed with the selection) or “uncertain” (in case of disagreement). In the case of “uncertain” classification, discrepancies were resolved by further examination performed by one of the three expert authors (A.M., X.M., or M.C.). We used a standardised electronic spreadsheet (Microsoft Excel, V 14.4.1; Microsoft, Redmond, WA) to extract data from all included studies, recording: the study setting (type of study, geographical area and time, where and when the study was carried out, and sample size), patient characteristics (gender, age, reason for admission, underlying diseases, ICU scores of severity, mode of ventilation, and inotropic/vasopressor support), criteria for haemodynamic instability, fluid challenge characteristics, pre- and post-fluid challenge haemodynamic variables. When necessary, the corresponding authors of the included studies were contacted to obtain missing data related to trial demographics, methods, and outcomes (Additional file 1 : Table S2).

Statistical analysis

Statistical analysis was conducted on the summary statistics described in the selected articles (e.g., means, medians, proportions) and, therefore, the statistical unit of observation for all the selected variables was the single study and not the patient. Due to the discrepancy between the overall patients enrolled in the trials over the two considered decaders, the comparisons were not weighted for study size.

Fluid challenge was the exposure variable, and clinical and haemodynamic characteristics were considered outcome variables. Descriptive statistics of individual studies used different statistical indicators for central tendency and variability, such as means and standard deviations (i.e., age, tidal volume, fluid responders, severity scores), whereas absolute and relative frequencies were adopted for qualitative variables. To show one indicator for the quantitative variables, we collected means with standard deviations (SD) or medians and inter-quartile ranges (IQR).

Student's t test or Mann–Whitney test in case of parametric or nonparametric distributions, respectively, were used to assess the difference in mean values between responders and non-responders.

Statistical analyses were conducted using GraphPad PRISM® 8 (GraphPad Software Inc., San Diego, CA, USA) and STATA®15 (StataCorp, College Station, TX, USA). For all comparisons, we considered p values < 0.05 significant.

The electronic search identified 3,963 potentially relevant studies. Figure  1 and Additional file 1 : Table S3 provide a detailed description of the selection process flow. After evaluating 160 full-text manuscripts, the inclusion criteria were met by 124 studies, 32 (25.8%) published in the period 2000–2010 and 92 (74.2%) in the period 2011–2021. Ten studies (8.1%) required revision by senior examiners because of disagreement regarding inclusion criteria between the initial examiners. We did not find any further relevant publications by reviewing the bibliography of the selected studies.

Flow of the studies; *Reasons for studies' exclusion are reported in the Supplementary materials

The general characteristics of the patients are reported in Table 1 . We included 6,086 patients, with a median (IQR) of 38 (30–59) patients enrolled in each study. Six studies (4.8%) [ 20 , 21 , 22 , 23 , 24 , 25 ] were retrospective, while the others were prospective. The median (IQR) period of enrolment [reported in 66 (52.8%) studies] was 12 (6–18) months. At baseline, 2,985 (49.0%) patients received norepinephrine, 179 (2.9%) dopamine, 416 (6.8%) dobutamine, and 177 (2.8%) epinephrine.

The reliability of a functional haemodynamic test in predicting fluid responsiveness was assessed in 46 (37.1%) studies. Comparing the two considered decades, no difference was found in the rate of FC administration [17 min (17–33) vs. 33 min (17–50); p  = 0.39), in the percentage of fluid responders [52% (43–67) vs. 53% (45–60); p  = 0.91], in the percentage of studies adopting crystalloids over colloids [63.6% vs. 67.9%; p  = 1.00), or in the threshold of increase in CO or surrogates adopted to define fluid responsiveness (10% over 15%) [18.2% vs. 24.1%; p  = 1.00).

Forty-four studies (35.4%) investigated the reliability of a dynamic index in predicting fluid responsiveness. Comparing the two considered decades, no differences were found in the rate of FC administration [17 min (17–25) vs. 29 min (13–33) p  = 0.42), or in the rate of fluid responders [53% (41–62) vs. 50% (44–56) p  = 0.81), or in the threshold of increase in CO or surrogates adopted to define fluid responsiveness (10% over 15%) (78.5% vs. 66.67 p  = 0.42), as compared to studies in the decade 2000–2010. On the contrary, in the decade 2010-2021 we adopted more frequently crystalloids (21.4% vs. 60.0% p  = 0.024).

Fluid challenge characteristics and haemodynamic monitoring

Overall, the included studies infused 6,333 fluid challenges. The median (IQR) proportion of fluid responders was 52 (44–62)% (Table 2 ).

In 19 studies (15.3%), the volume of the fluid challenge was reported in mL/kg, with a median (IQR) of 7 (6–8) mL/kg (Table 2 ). A fixed volume of 500 mL was administered in 95 (76.6)% of the included studies. The median (IQR) of the dispensed volume of fluid was 500 (500–500) mL, infused in a median (IQR) of 18 (11–30) min. Then, the median (IQR) infusion rate was 25 (17–33) mL/min.

CO/CI was used as target variables in 78 (62.9%) studies, while SV/SVI was used in 40 (32.2%) studies. The other six studies (4.8%) adopted SV surrogates (ABF in 4 studies and VTI in two studies). In 88 (70.9%) studies, the threshold adopted to define the fluid responsiveness was an increase of the considered variable ≥ 15% from baseline (Table 2 ).

Three studies (2.4%) [ 25 , 26 , 27 ] did not report the type of fluid used for the fluid challenge. Among the others, crystalloids were used in 68 (56.6)% studies, colloids in 52 (43.3) %, and blood in one (0.8)% (Table 2 ).

The majority of the studies [49 (39.5%)] used transpulmonary thermodilution/dye dilution calibrated haemodynamic monitoring; 22 (17.7%) studies adopted the pulmonary artery catheter monitoring. Echocardiography (either transthoracic or transoesophageal) was used in 31 (25.0)% of studies, and 5 (4.0%) used oesophageal doppler monitoring. Uncalibrated pulse wave analysis monitoring was used in the other 14 (11.2)% studies (Table 2 ). Finally, bioreactance was adopted in three studies (2.4%). Haemodynamic pre–post-fluid challenge variables in responders and non-responders populations are reported in Table 3 .

Trigger of fluid challenge administration.

Hypotension (i.e., systolic or mean arterial pressure below a fixed value or reduced by a fixed percentage from baseline) was used in 68 (62.4)% of studies. Oliguria (i.e. a drop in urine output below 0.5 mL/h for 2 or 3 consecutive hours) was used in 54 (49.5)% studies, skin mottling or peripheral hypoperfusion in 47 (43.1)% studies, tachycardia (i.e. an increase in heart rate above 100–110 beats/min) in 43 (39.4)%, the need for initiating the infusion or reducing the dose of vasoactive drugs in 41 (37.6)% studies, an increase in blood lactate in 34 (31.2)% studies, a diagnosis of sepsis/septic shock in 12 (11.0)% studies, and renal or hepatic dysfunction in seven (6.4)% studies. Fifteen studies (12.1%) did not report any trigger to start fluid challenge administration.

Comparison of publication periods 2011–2021 versus 2000–2010

The comparison between the 2000–2010 and 2011–2021 decades is reported in Table 4 . The percentage of fluid responders (52% for both the decades) and the volume infused (500 mL) were comparable. On the contrary, the infusion time was lower in the last decade (a median of 15 (10–30) min vs 30 (15–30) min, p  = 0.03). Crystalloids were used in 61.9% of studies published between 2011–2021 and 34.3% in the 2000–2010 decade ( p  = 0.007) (Figs.  2 and S1 in the Additional file 1 ).

Percentage of studies in the two decades adopting different infusion timings. Fluid challenge, fluid challenge

CO/CI was used in 67% of the studies published in 2011–2021 and in 60% of those published in 2000–2010 ( p  = 0.51). The threshold adopted was an increase in CO or surrogates ≥ 15% in 67.4% of the studies of the 2011–2021 decade and in 81.2% of the studies published in 2000–2010 ( p  = 0.17) (Additional file 1 : Figure S1).

The results of this review, including research studies investigating the fluid challenge effect in critically ill adult patients receiving haemodynamic monitoring, may be summarised as follows: 1) fluid challenge is usually performed infusing a bolus of 500 mL of fluid, most often a crystalloid, in less than 20 min; 2) the response to fluid challenge is usually defined as a CI or CO increase ≥ 15% as compared to baseline; 3) positive response to fluid challenge is reported in about 50% of ICU patients; 4) the most common trigger for fluid challenge administration is usually the occurrence of hypotension, followed by oliguria and clinical signs of hypoperfusion; 5) the comparison between the 2000–2010 and 2011–2021 decades of publication showed no difference in the percentage of fluid responders (52% on average for both the decades), the volume infused (500 ml), and the criteria defining fluid responsiveness. On the contrary, compared to the 2000–2010 decade, in the period 2011–2021, the fluid challenge infusion time was lower, and crystalloids were more frequently used.

Fluid challenge characteristics

Among the included studies, the fluid challenge usually consisted of a median volume of 500 mL administered over a 20-min period and defined as a positive response by an increase ≥ 15% of CO or surrogate. These characteristics and responsiveness definition are to be considered good practice, for the response of CO to a fluid bolus is poorly followed by the simultaneous changes in arterial pressure [ 28 , 29 ] or heart rate [ 30 ]. However, this is not the case in clinical practice, where the fluid challenge effect is often assessed by a rise in arterial blood pressure [ 16 ].

Interestingly, 500 mL was also the median volume fluid challenge used in the FENICE study (an observational study including 311 centres across 46 countries) [ 16 ], whereas a fluid challenge of 250 mL is usually adopted in high-risk surgical patients undergoing goal-directed therapy optimisation [ 31 ]. The use of large volumes for fluid challenge optimisation should be balanced to the detrimental risk of fluid overload [ 9 ], primarily if safety limits (i.e. , increase in CVP) dynamically indicate fluid non-responsiveness are rarely used [ 19 ]. Since fluid challenge volume should be at least 4 mL/kg [ 32 ], smaller fluid challenge volumes may be considered for repetitive tests.

Moreover, the FENICE study reported a median of 24 min of infusion time and a rate of 17 mL/min [ 16 ]. Hence, the volume and rate of administration seem comparable between clinical and research settings. On the contrary, the infusion time was lower in the last decade (a median of 15 min vs 30 min, p  = 0.03), indicating a trend towards the increase in the infusion rate in more recent studies. This global inception cohort study evaluated the clinical use of the fluid challenge in daily practice, whereas our review considered only research papers adopting the fluid challenge as a part of a protocol, limiting the comparison with the results of the FENICE. Moreover, in contrast with a previous metanalysis, including ICU studies up to 2014 [ 19 ], crystalloids are used in most studies. Crystalloids have been used in two-thirds of the studies from 2011 to 2021, compared to one-third from 2000 to 2010. These data indicate an alignment between research studies, recent guidelines, and metanalyses [ 13 , 14 ].

Limitations

Limitations of our review have to be considered when extrapolating the results to clinical practice. First, the present study does not report any outcome endpoints. A recent large randomised-controlled trial showed no difference in mortality rate among ICU patients receiving different fluid bolus infusion rates [ 33 ]. However, the faster rate adopted in this study (5.5 mL/min) is below the median rate found in the studies included in the present review (25 mL/min) [ 33 ]. The administration of aliquots of fluids at a slow rate should not probably be indicated as a fluid challenge. Moreover, all the included studies are research papers whose aim was to evaluate the haemodynamic changes after the fluid challenge infusion or assess the reliability of indexes or functional haemodynamic tests in predicting the response to a fluid challenge. We did not include studies on the fluid challenge clinical use in ICU patients.

Another potential source of bias is related to the different haemodynamic monitorings used to assess fluid challenge responsiveness. When considering the median cut-off value identifying responders from non-responders, the accuracy of measurement of the changes in CO, or its surrogates, is undoubtedly relevant. Additionally, the reliability of different monitorings in tracking the dynamic trends of CO may not be consistent and may be below the boundaries of accuracy and precision of the Critchley–Critchley criteria [ 34 ]. Hence, the reproducibility of CO measurements obtained by the different monitoring systems may be limited. Moreover, cut-off values and measurement techniques potentially induce heterogeneity in response to the fluid challenge administration. As confirmed, responders ranged from 23 to 100% across the included studies (Table 2 ). The use of echocardiography is associated with high proportions of fluid responders compared to other haemodynamic monitoring devices. The operator-dependent bias may affect the evaluation of SV changes after fluid challenge.

We excluded studies in which the fluid challenge response has been assessed without haemodynamic monitoring and, hence assessing changes in systemic arterial pressures, potentially limiting the whole comparability of the technique in the two considered decades. Finally, the overall number of patients enrolled in the trials of the two considered decades was considerably different. This could bias the comparisons between the two groups if weighted for study size.

This systematic review, including research studies on fluid challenge use in critically ill adult patients receiving haemodynamic monitoring, showed a positive response in 52% of the patients. This test was usually performed infusing a bolus of 500 mL fluid, more often a crystalloid, in less than 20 min, and fluid responsiveness was generally indicated as a CI or CO increase ≥ 15% compared to baseline. Fluid challenge administration is usually triggered by hypotension. In the 2011–2021, the infusion time was shorter, and crystalloids were more frequently used than in the 2000–2010 decade.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Cardiac index

Stroke volume index

Cardiac output

Stroke volume

Intensive care unit

Central venous pressure

Velocity–time integral in the left ventricular outflow tract

Aortic blood flow

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Acknowledgements

We are thankful to Dr. Katerina Negri for the linguistic revision of this manuscript.

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Department of Anesthesia and Intensive Care Medicine, Humanitas Clinical and Research Center—IRCCS, Via Alessandro Manzoni, 56, 20089, Rozzano, Milano, Italy

Antonio Messina, Lorenzo Calabrò, Luca Pugliese, Aulona Lulja, Alexandra Sopuch, Emanuela Morenghi & Maurizio Cecconi

Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Milano, Italy

Antonio Messina, Emanuela Morenghi & Maurizio Cecconi

Università del Piemonte Orientale, Vercelli, Italy

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Hôpitaux Universitaires Paris-Sud, Hôpital de Bicêtre, Medical Intensive Care Unit, Le Kremlin-Bicêtre, F-94270, Paris, France

Xavier Monnet

Université Paris-Saclay, AP-HP, Service de médecine intensive-réanimation, Hôpital de Bicêtre, Paris, France

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AM designed the study, performed data analysis, and drafted the manuscript; EM: helped in data analysis and manuscript preparation; LC, LP, AL, AS, and DR substantially contributed to data collection and interpretation; MC, XM, and GE substantially contributed to data interpretation and manuscript draft. All the authors approved the final version of the paper and agreed to be accountable for all aspects of the work, thereby ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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Dr. Messina received travel expenses and registration for meetings, congresses, and courses and lecture fees from Vygon, Edwards, Philips, and Getinge. Xavier Monnet is a member of the medical advisory board of Pulsion Medical Systems (Getinge), and has given lectures for Baxter. Prof. Cecconi is a consultant of Edwards Lifesciences (Directed Systems Consultancy).

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Additional file 1.

. Table S1. PRISMA-DTA checklist. Table S2. Extracted data in each study assessed for eligibility. Table S3. Full-text articles excluded, not fitting eligibility criteria. Table S4. Studies on functional haemodynamic tests or dynamic indexes of fluid responsiveness. Figure S1.  Characteristics of fluid challenge administration and monitoring along the considered years.

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Messina, A., Calabrò, L., Pugliese, L. et al. Fluid challenge in critically ill patients receiving haemodynamic monitoring: a systematic review and comparison of two decades. Crit Care 26 , 186 (2022). https://doi.org/10.1186/s13054-022-04056-3

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Once Upon a Time, the World of Picture Books Came to Life

The tale behind a new museum of children’s literature is equal parts imagination, chutzpah and “The Little Engine That Could.”

By Elisabeth Egan

Photographs and Video by Chase Castor

Elisabeth Egan followed the Rabbit Hole as it was nearing completion. She has written about several of its inhabitants for The Times.

On a crisp Saturday morning that screamed for adventure, a former tin can factory in North Kansas City, Mo., thrummed with the sound of young people climbing, sliding, spinning, jumping, exploring and reading.

Yes, reading.

If you think this is a silent activity, you haven’t spent time in a first grade classroom. And if you think all indoor destinations for young people are sticky, smelly, depressing hellholes, check your assumptions at the unmarked front door.

Welcome to the Rabbit Hole, a brand-new, decade-in-the-making museum of children’s literature founded by the only people with the stamina for such a feat: former bookstore owners. Pete Cowdin and Deb Pettid are long-married artists who share the bullish determination of the Little Red Hen. They’ve transformed the hulking old building into a series of settings lifted straight from the pages of beloved picture books.

Before we get into what the Rabbit Hole is, here’s what it isn’t: a place with touch screens, a ball pit, inscrutable plaques, velvet ropes, a cloying soundtrack or adults in costumes. It doesn’t smell like graham crackers, apple juice or worse (yet). At $16 per person over 2 years old, it also isn’t cheap.

During opening weekend on March 16, the museum was a hive of freckles and gap toothed grins, with visitors ranging in age from newborn to well seasoned. Cries of “Look up here!,” “There’s a path we need to take!” and “There’s Good Dog Carl !” created a pleasant pandemonium. For every child galloping into the 30,000 square foot space, there was an adult hellbent on documenting the moment.

Did you ever have to make a shoe box diorama about your favorite book? If so, you might remember classmates who constructed move-in ready mini kingdoms kitted out with gingham curtains, clothespin people and actual pieces of spaghetti.

Cowdin, Pettid and their team are those students, all grown up.

The main floor of the Rabbit Hole consists of 40 book-themed dioramas blown up to life-size and arranged, Ikea showroom-style, in a space the size of two hockey rinks. The one inspired by John Steptoe’s “ Uptown ” features a pressed tin ceiling, a faux stained-glass window and a jukebox. In the great green room from “ Goodnight Moon ,” you can pick up an old-fashioned phone and hear the illustrator’s son reading the story.

One fictional world blends into the next, allowing characters to rub shoulders in real life just as they do on a shelf. Visitors slid down the pole in “The Fire Cat,” slithered into the gullet of the boa constrictor in “ Where the Sidewalk Ends ” and lounged in a faux bubble bath in “ Harry the Dirty Dog .” There are plenty of familiar faces — Madeline , Strega Nona , Babar — but just as many areas dedicated to worthy titles that don’t feature household names, including “ Crow Boy ,” “ Sam and the Tigers ,” “ Gladiola Garden ” and “ The Zabajaba Jungle .”

Emma Miller, a first-grade teacher, said, “So many of these are books I use in my classroom. It’s immersive and beautiful. I’m overwhelmed.”

As her toddler bolted toward “ Frog and Toad ,” Taylar Brown said, “We love opportunities to explore different sensory things for Mason. He has autism so this is a perfect place for him to find little hiding holes.”

A gaggle of boys reclined on a bean bag in “ Caps for Sale ,” passing around a copy of the book. Identical twins sounded out “ Bread and Jam for Frances ” on the pink rug in the badger’s house. A 3-year-old visiting for the second time listened to her grandfather reading “The Tawny Scrawny Lion.”

Tomy Tran, a father of three from Oklahoma, said, “I’ve been to some of these indoor places and it’s more like a jungle gym. Here, my kids will go into the area, pick up the book and actually start reading it as if they’re in the story.”

All the titles scattered around the museum are available for purchase at the Lucky Rabbit, a bookstore arranged around a cozy amphitheater. Pettid and Cowdin estimate that they’ve sold one book per visitor, with around 650 guests per day following the pink bunny tracks from the parking lot.

Once upon a time, Cowdin and Pettid owned the Reading Reptile, a Kansas City institution known not just for its children’s books but also for its literary installations. When Dav Pilkey came to town, Pettid and Cowdin welcomed him by making a three-and-a-half foot papier-mâché Captain Underpants. Young customers pitched in to build Tooth-Gnasher Superflash or the bread airplane from “In the Night Kitchen.”

One of the store’s devotees was Meg McMath, who continued to visit through college, long after she’d outgrown its offerings (and its chairs). Now 36, McMath traveled from Austin, Texas with her husband and six-month-old son to see the Rabbit Hole. “I’ve cried a few times,” she said.

The Reading Reptile weathered Barnes & Noble superstores and Amazon. Then came “the Harry Potter effect,” Pettid said, “where all of a sudden adults wanted kids to go from picture books to thick chapter books. They skipped from here to there; there was so much they were missing.”

As parents fell under the sway of reading lists for “gifted” kids, story time became yet another proving ground.

“It totally deformed the reading experience,” Cowdin said. Not to mention the scourge of every bookstore: surreptitious photo-snappers who later shopped online.

In 2016, Cowdin and Pettid closed the Reptile to focus on the Rabbit Hole, an idea they’d been percolating for years. They hoped it would be a way to spread the organic bookworm spirit they’d instilled in their five children while dialing up representation for readers who had trouble finding characters who looked like them. The museum would celebrate classics, forgotten gems and quality newcomers. How hard could it be?

Cowdin and Pettid had no experience in the nonprofit world. They knew nothing about fund-raising or construction. They’re ideas people, glass half full types, idealists but also stubborn visionaries. They didn’t want to hand their “dream” — a word they say in quotes — to consultants who knew little about children’s books. Along the way, board members resigned. Their kids grew up. Covid descended. A tree fell on their house and they had to live elsewhere for a year. “I literally have told Pete I quit 20 times,” Pettid said.

“It has not always been pleasant,” Cowdin said. “But it was just like, OK, we’re going to do this and then we’re going to figure out how to do it. And then we just kept figuring it out.”

Little by little, chugging along like “ The Little Engine That Could ,” they raised $15 million and assembled a board who embraced their vision and commitment to Kansas City. They made a wish list of books — “Every ethnicity. Every gender. Every publisher,” Pettid said — and met with rights departments and authors’ estates about acquiring permissions. Most were receptive; some weren’t. (They now have rights to more than 70 titles.)

“A lot of people think a children’s bookstore is very cute,” Pettid said. “They have a small mind for children’s culture. That’s why we had to buy this building.”

For $2 million, they bought the factory from Robert Riccardi, an architect whose family operated a beverage distribution business there for two decades. His firm, Multistudio, worked with Cowdin and Pettid to reimagine the space, which sits on an industrial corner bordered by train tracks, highways and skyline views.

Cowdin and Pettid started experimenting with layouts. Eventually they hired 39 staff members, including 21 full-time artists and fabricators who made everything in the museum from some combination of steel, wood, foam, concrete and papier-mâché.

“My parents are movers and shakers,” Gloria Cowdin said. She’s the middle of the five siblings, named after Frances the badger’s sister — and, yes, that’s her voice reading inside the exhibit. “There’s never been something they’ve wanted to achieve that they haven’t made happen, no matter how crazy.”

During a sneak peek in December, it was hard to imagine how this semi-construction zone would coalesce into a museum. The 22,000 square foot fabrication section was abuzz with drills and saws. A whiteboard showed assembly diagrams and punch lists. (Under “Random jobs,” someone had jotted, “Write Christmas songs.”) The entryway and lower level — known as the grotto and the burrow — were warrens of scaffolding and machinery.

But there were pockets of calm. Kelli Harrod worked on a fresco of trees outside the “ Blueberries for Sal ” kitchen, unfazed by the hubbub. In two years as lead painter, she’d witnessed the Rabbit Hole’s steady growth.

“I remember painting the ‘ Pérez and Martina ’ house before there was insulation,” Harrod said. “I was bundled up in hats, gloves and coats, making sure my hands didn’t shake.”

Leigh Rosser was similarly nonplused while describing his biggest challenge as design fabrication lead. Problem: How to get a dragon and a cloud to fly above a grand staircase in “ My Father’s Dragon .” Solution: “It’s really simple, conceptually” — it didn’t sound simple — “but we’re dealing with weight in the thousands of pounds, mounted up high. We make up things that haven’t been done before, or at least that I’m not aware of.”

Attention to detail extends to floor-bound exhibits. The utensil drawer in “Blueberries for Sal” holds Pete Cowdin’s mother’s egg whisk alongside a jar containing a baby tooth that belonged to Cowdin and Pettid’s oldest daughter, Sally. The tooth is a wink at “ One Morning in Maine ,” an earlier Robert McCloskey book involving a wiggly bicuspid — or was it a molar? If dental records are available, Cowdin and Pettid have consulted them for accuracy.

“With Pete and Deb, it’s about trying to picture what they’re seeing in their minds,” said Brian Selznick , a longtime friend who helped stock the shelves in the Lucky Rabbit. He’s the author of “ The Invention of Hugo Cabret ,” among many other books.

Three months ago, the grotto looked like a desert rock formation studded with pink Chiclets. The burrow, home of Fox Rabbit, the museum’s eponymous mascot, was dark except for sparks blasting from a soldering iron. The floor was covered with tiny metal letters reclaimed from a newly-renovated donor wall at a local museum.

Cowdin and Pettid proudly explained their works-in-progress; these were the parts of the museum that blossomed from seed in their imaginations. But to the naked eye, they had the charm of a bulkhead door leading to a scary basement.

When the museum opened to the public, the grotto and the burrow suddenly made sense. The pink Chiclets are books, more than 3000 of them — molded in silicone, cast in resin — incorporated into the walls, the stairs and the floor. They vary from an inch-and-a-half to three inches thick. As visitors descend into the Rabbit Hole, they can run their fingers over the edges of petrified volumes. They can clamber over rock formations that include layers of books. Or they can curl up and read.

Dennis Butt, another longtime Rabbit Hole employee, molded 92 donated books into the mix, including his own copies of “ The Hobbit ” and “ The Lord of the Rings .” He said, “They’re a little piece of me.”

As for the metal letters, they’re pressed into the walls of a blue-lit tunnel leading up a ramp to the first floor. They spell the first lines of 141 books, including “ Charlotte’s Web ,” “Devil in the Drain” and “ Martha Speaks .” Some were easier to decipher than others, but “Mashed potatoes are to give everybody enough” jumped out. It called to mind another line from “A Hole is to Dig,” Ruth Krauss’s book of first definitions (illustrated by a young Maurice Sendak ): “The world is so you have something to stand on.”

At the Rabbit Hole, books are so you have something to stand on. They’re the bedrock and the foundation; they’re the solid ground.

Cowdin and Pettid have plans to expand into three more floors, adding exhibit space, a print shop, a story lab, a resource library and discovery galleries. An Automat-style cafeteria and George and Martha -themed party and craft room will open soon. A rooftop bar is also in the works.

Of course, museum life isn’t all happily ever after. Certain visitors whined, whinged and wept, especially as they approached the exit. One weary adult said, “Charlie, we did it all.”

Then, “Charlie, it’s time to go.”

And finally, “Fine, Charlie, we’re leaving you here.” Cue hysteria.

But the moral of this story — and the point of the museum, and maybe the point of reading, depending on who you share books with — crystallized in a quiet moment in the great green room. A boy in a Chiefs Super Bowl T-shirt pretended to fall asleep beneath a fleecy blanket. Before closing his eyes, he said, “Goodnight, Grandma. Love you to the moon.”

Elisabeth Egan is a writer and editor at the Times Book Review. She has worked in the world of publishing for 30 years. More about Elisabeth Egan

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