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APA Citation Style

Citation examples.

• Paper Format
• Style and Grammar Guidelines
• Citation Management Tools
• What's New in the 7th Edition?
• APA Style References Guidelines from the American Psychological Association
• APA Style (OWL - Online Writing Lab, Purdue University)
• Common Reference Examples Handout
• Journal Article
• Magazine Article
• Newspaper Article
• Edited Book Chapter
• Dictionary Entry
• Government Report
• YouTube Video
• Facebook Post
• Webpage on a Website
• Supplemental Reference Examples
• Archival Documents and Collections

Parenthetical citations:  (Grady et al., 2019; Jerrentrup et al., 2018)

Narrative citations:  Grady et al. (2019) and Jerrentrup et al. (2018)

• If a journal article has a DOI, include the DOI in the reference.
• If the journal article does not have a DOI and is from an academic research database, end the reference after the page range (for an explanation of why, see the  database information  page). The reference in this case is the same as for a print journal article.
• Do not include database information in the reference unless the journal article comes from a database that publishes original, proprietary content, such as UpToDate (see an example on the  database information  page).
• If the journal article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online journal that is not part of a database), include the URL of the article at the end of the reference.
• If the journal article has an article number instead of a page range, include the article number instead of the page range (as shown in the Jerrentrup et al. example).

Parenthetical citations:  (Rabinowitz, 2019; Sapolsky, 2017)

Narrative citations:  Rabinowitz (2019) and Sapolsky (2017)

• If the book includes a DOI, include the DOI in the reference after the publisher name.
• Do not include the publisher location.
• If the book does not have a DOI and comes from an academic research database, end the book reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print book.

Parenthetical citations:  (Schaefer & Shapiro, 2019; Schulman, 2019)

Narrative citations:  Schaefer and Shapiro (2019) and Schulman (2019)

• If a magazine article has a DOI, include the DOI in the reference.
• If the magazine article does not have a DOI and is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print magazine article.
• If the magazine article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online magazine that is not part of a database), include the URL of the article at the end of the reference.
• If the magazine article does not have volume, issue, and/or page numbers (e.g., because it is from an online magazine), omit the missing elements from the reference (as in the Schulman example).

Parenthetical citation:  (Carey, 2019)

Narrative citation:  Carey (2019)

• If the newspaper article is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print newspaper article.
• If the newspaper article has a URL that will resolve for readers (e.g., it is from an online newspaper), include the URL of the article at the end of the reference.
• If the newspaper article does not have volume, issue, and/or page numbers (e.g., because it is from an online newspaper), omit the missing elements from the reference, as shown in the example.
• If the article is from a news website (e.g., CNN, HuffPost)—one that does not have an associated daily or weekly newspaper—use the format for a  webpage on a website  instead.

Parenthetical citation:  (Aron et al., 2019)

Narrative citation:  Aron et al. (2019)

• If the edited book chapter includes a DOI, include the chapter DOI in the reference after the publisher name.
• If the edited book chapter does not have a DOI and comes from an academic research database, end the edited book chapter reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print edited book chapter.
• Do not create references for chapters of authored books. Instead, write a reference for the whole book and cite the chapter in the text if desired (e.g., Kumar, 2017, Chapter 2).

Parenthetical citation:  (Merriam-Webster, n.d.)

Narrative citation:  Merriam-Webster (n.d.)

• Because entries in  Merriam-Webster’s Dictionary  are updated over time and are not archived, include a  retrieval date  in the reference.
• Merriam-Webster is both the author and the publisher, so the name appears in the author element only to avoid repetition.
• To quote a dictionary definition, view the pages on quotations and  how to quote works without page numbers  for guidance. Additionally, here is an example:  Culture  refers to the “customary beliefs, social forms, and material traits of a racial, religious, or social group” (Merriam-Webster, n.d., Definition 1a).

Parenthetical citation:  (National Cancer Institute, 2019)

Narrative citation:  National Cancer Institute (2019)

The specific agency responsible for the report appears as the author. The names of parent agencies not present in the  group author name  appear in the source element as the publisher. This creates concise in-text citations and complete reference list entries.

Parenthetical citation:  (Harvard University, 2019)

Narrative citation:  Harvard University (2019)

• Use the name of the account that uploaded the video as the author.
• If the account did not actually create the work, explain this in the text if it is important for readers to know. However, if that would mean citing a source that appears unauthoritative, you might also look for the author’s YouTube channel, official website, or other social media to see whether the same video is available elsewhere.

Parenthetical citations:  (APA Databases, 2019; Gates, 2019)

Narrative citations:  APA Databases (2019) and Gates (2019)

• Present the name of the individual or group author the same as you would for any other reference. Then provide the Twitter handle (beginning with the @ sign) in square brackets, followed by a period.
• Provide the first 20 words of the tweet as the title. Count a URL, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words.
• If the tweet includes an image, a video, a poll, or a thumbnail image with a link, indicate that in brackets after the title: [Image attached], [Video attached], [Thumbnail with link attached].
• The same format used for Twitter is also used for Instagram.  

Parenthetical citation:  (News From Science, 2019)

Narrative citation:  News From Science (2019)

• Provide the first 20 words of the Facebook post as the title. Count a URL or other link, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words. 
• If a status update includes images, videos, thumbnail links to outside sources, or content from another Facebook post (such as when sharing a link), indicate that in square brackets.

Parenthetical citations:  (Fagan, 2019; National Institute of Mental Health, 2018; Woodyatt, 2019; World Health Organization, 2018)

Narrative citations:  Fagan (2019), National Institute of Mental Health (2018), Woodyatt (2019), and World Health Organization (2018)

• Provide as specific a  date  as is available on the webpage. This might be a year only; a year and month; or a year, month, and day.
• Italicize the title of a webpage.
• When the author of the webpage and the publisher of the website are the same, omit the publisher name to avoid repetition (as in the World Health Organization example).
• When contents of a page are meant to be updated over time but are not archived, include a  retrieval date  in the reference (as in the Fagan example).
• Use the webpage on a website format for articles from news websites such as CNN and HuffPost (these sites do not have associated daily or weekly newspapers). Use the  newspaper article category  for articles from newspaper websites such as  The New York Times  or  The Washington Post .
• Create a reference to an open educational resources (OER) page only when the materials are available for download directly (i.e., the materials are on the page and/or can be downloaded as PDFs or other files). If you are directed to another website, create a reference to the specific webpage on that website where the materials can be retrieved. Use this format for material in any OER repository, such as OER Commons, OASIS, or MERLOT.
• Do not create a reference or in-text citation for a whole website. To mention a website in general, and not any particular information on that site, provide the name of the website in the text and include the URL in parentheses. For example, you might mention that you used a website to create a survey.

The following supplemental example references are mention in the  Publication Manual:

• retracted journal or magazine article
• edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM)
• edition of the International Statistical Classification of Diseases and Related Health Problems (ICD)
• religious work
• annotated religious work

Archival document and collections are not presented in the  APA Publication Manual, Seventh Edition . This content is available only on the APA Style website .  This guidance has been expanded from the 6th edition.

Archival sources include letters, unpublished manuscripts, limited-circulation brochures and pamphlets, in-house institutional and corporate documents, clippings, and other documents, as well as such nontextual materials as photographs and apparatus, that are in the personal possession of an author, form part of an institutional collection, or are stored in an archive such as the Archives of the History of American Psychology at the University of Akron or the APA Archives. For any documents like these that are available on the open web or via a database (subscription or nonsubscription), follow the reference templates shown in Chapter 10 of the Publication Manual.

The general format for the reference for an archival work includes the author, date, title, and source. The reference examples shown on this page may be modified for collections requiring more or less specific information to locate materials, for different types of collections, or for additional descriptive information (e.g., a translation of a letter). Authors may choose to list correspondence from their own personal collections, but correspondence from other private collections should be listed only with the permission of the collector.

Keep in mind the following principles when creating references to archival documents and collections:

• As with any reference, the purpose is to direct readers to the source, despite the fact that only a single copy of the document may be available and readers may have some difficulty actually seeing a copy.
• Include as much information as is needed to help locate the item with reasonable ease within the repository. For items from collections with detailed finding aids, the name of the collection may be sufficient; for items from collections without finding aids, more information (e.g., call number, box number, file name or number) may be necessary to help locate the item.
• If several letters are cited from the same collection, list the collection as a reference and provide specific identifying information (author, recipient, and date) for each letter in the in-text citations (see Example 3).
• Use square brackets to indicate information that does not appear on the document.
• Use “ca.” (circa) to indicate an estimated date (see Example 5).
• Use italics for titles of archival documents and collections; if the work does not have a title, provide a description in square brackets without italics.
• Separate elements of the source (e.g., the name of a repository, library, university or archive, and the location of the university or archive) with commas. End the source with a period.
• If a publication of limited circulation is available in libraries, the reference may be formatted as usual for published material, without the archival source.
• Note that private letters (vs. those in an archive or repository) are considered personal communications and cited in the text only.

1. Letter from a repository

Frank, L. K. (1935, February 4). [Letter to Robert M. Ogden]. Rockefeller Archive Center (GEB Series 1.3, Box 371, Folder 3877), Tarrytown, NY, United States.

• Parenthetical citation: (Frank, 1935)
• Narrative citation: Frank (1935)
• Because the letter does not have a title, provide a description in square brackets.

2. Letter from a private collection

Zacharius, G. P. (1953, August 15). [Letter to William Rickel (W. Rickel, Trans.)]. Copy in possession of Hendrika Vande Kemp.

• Parenthetical citation: (Zacharius, 1953)
• Narrative citation: Zacharius (1953)
• In this example, Hendrika Vande Kemp is either the author of the paper or the author of the paper has received permission from Hendrika Vande Kemp to cite a letter in Vande Kemp’s private collection in this way. Otherwise, cite a private letter as a  personal communication .

3. Collection of letters from an archive

Allport, G. W. (1930–1967). Correspondence. Gordon W. Allport Papers (HUG 4118.10), Harvard University Archives, Cambridge, MA, United States.

• Parenthetical citation: (Allport, 1930–1967)
• Narrative citation: Allport (1930–1967)

To cite specific letters in the text, provide the author and range of years as shown in the reference list entry, plus details about who wrote the specific letter to whom and when the specific letter was written.

• Parenthetical citation: (Allport, 1930–1967, G. Boring to Allport, December 26, 1937)
• Narrative citation: Allport (1930–1967, Allport to G. Boring, March 1, 1939)
• Use the parenthetical citation format to cite a letter that E. G. Boring wrote to Allport because Allport is the author in the reference. Use either the parenthetical or narrative citation format to cite letters that Allport wrote.

4. Unpublished papers, lectures from an archive or personal collection

Berliner, A. (1959). Notes for a lecture on reminiscences of Wundt and Leipzig. Anna Berliner Memoirs (Box M50), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

• Parenthetical citation: (Berliner, 1959)
• Narrative citation: Berliner (1959)

5. Archival/historical source for which the author and/or date is known or is reasonably certain but not stated on the document

Allport, A. (presumed). (ca. 1937). Marion Taylor today—by the biographer [Unpublished manuscript]. Marion Taylor Papers, Schlesinger Library, Radcliffe College, Cambridge, MA, United States.

• Parenthetical citation: (Allport, ca. 1937)
• Narrative citation: Allport (ca. 1937)
• Because the author is reasonably certain but not stated on the document, place the word “presumed” in parentheses after the name, followed by a period.
• Because the date is reasonably certain but not stated on the document, the abbreviation “ca.” (which stands for “circa”) appears before the year in parentheses.

6. Archival source with group author

Subcommittee on Mental Hygiene Personnel in School Programs. (1949, November 5–6). Meeting of Subcommittee on Mental Hygiene Personnel in School Programs. David Shakow Papers (M1360), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

• Parenthetical citation: (Subcommittee on Mental Hygiene Personnel in School Programs, 1949)
• Narrative citation: Subcommittee on Mental Hygiene Personnel in School Programs (1949)

7. Interview recorded and available in an archive

Smith, M. B. (1989, August 12). Interview by C. A. Kiesler [Tape recording]. President’s Oral History Project, American Psychological Association, APA Archives, Washington, DC, United States.

• Parenthetical citation: (Smith, 1989)
• Narrative citation: Smith (1989)
• For interviews and oral histories recorded in an archive, list the interviewee as the author. Include the interviewer’s name in the description.

8. Transcription of a recorded interview, no recording available

Sparkman, C. F. (1973). An oral history with Dr. Colley F. Sparkman/Interviewer: Orley B. Caudill. Mississippi Oral History Program (Vol. 289), University of Southern Mississippi, Hattiesburg, MS, United States.

• Parenthetical citation: (Sparkman, 1973)
• Narrative citation: Sparkman (1973)

9. Newspaper article clipping, historical, in personal collection

Psychoanalysis institute to open. (1948, September 18). [Clipping from an unidentified Dayton, OH, United States, newspaper]. Copy in possession of author.

• Parenthetical citation: (“Psychoanalysis Institute to Open,” 1948)
• Narrative citation: “Psychoanalysis Institute to Open” (1948)
• Use this format only if you are the person who is in possession of the newspaper clipping.

10. Historical publication of limited circulation

Sci-Art Publishers. (1935). Sci-Art publications [Brochure]. Roback Papers (HUGFP 104.50, Box 2, Folder “Miscellaneous Psychological Materials”), Harvard University Archives, Cambridge, MA, United States.

• Parenthetical citation: (Sci-Art Publishers, 1935)
• Narrative citation: Sci-Art Publishers (1935)

11. Archived photographs, no author and no title

[Photographs of Robert M. Yerkes]. (ca. 1917–1954). Robert Mearns Yerkes Papers (Box 137, Folder 2292), Manuscripts and Archives, Yale University Library, New Haven, CT, United States.

• Parenthetical citation: ([Photographs of Robert M. Yerkes], ca. 1917–1954)
• Narrative citation: [Photographs of Robert M. Yerkes] (ca. 1917–1954)
• Because the archived photographs do not have a title, provide a bracketed description instead.
• Because the archived photographs do not have an author, move the bracketed description to the author position of the reference.

12. Microfilm

U.S. Census Bureau. (1880). 1880 U.S. census: Defective, dependent, and delinquent classes schedule: Virginia [Microfilm]. NARA Microfilm Publication T1132 (Rolls 33–34), National Archives and Records Administration, Washington, DC, United States.

• Parenthetical citation: (U.S. Census Bureau, 1880)
• Narrative citation: U.S. Census Bureau (1880)

Read the full APA guidelines on citing ChatGPT 

OpenAI. (2023).  ChatGPT  (Mar 14 version) [Large language model].  https://chat.openai.com/chat

• Parenthetical citation:  (OpenAI, 2023)
• Narrative citation:  OpenAI (2023)

Author:  The author of the model is OpenAI.

Date:  The date is the year of the version you used. Following the template in Section 10.10, you need to include only the year, not the exact date. The version number provides the specific date information a reader might need.

Title:  The name of the model is “ChatGPT,” so that serves as the title and is italicized in your reference, as shown in the template. Although OpenAI labels unique iterations (i.e., ChatGPT-3, ChatGPT-4), they are using “ChatGPT” as the general name of the model, with updates identified with version numbers.

The version number is included after the title in parentheses. The format for the version number in ChatGPT references includes the date because that is how OpenAI is labeling the versions. Different large language models or software might use different version numbering; use the version number in the format the author or publisher provides, which may be a numbering system (e.g., Version 2.0) or other methods.

Bracketed text  is used in references for additional descriptions when they are needed to help a reader understand what’s being cited. References for a number of common sources, such as journal articles and books, do not include bracketed descriptions, but things outside of the typical peer-reviewed system often do. In the case of a reference for ChatGPT, provide the descriptor “Large language model” in square brackets. OpenAI describes ChatGPT-4 as a “large multimodal model,” so that description may be provided instead if you are using ChatGPT-4. Later versions and software or models from other companies may need different descriptions, based on how the publishers describe the model. The goal of the bracketed text is to briefly describe the kind of model to your reader.

Source:  When the publisher name and the author name are the same, do not repeat the publisher name in the source element of the reference, and move directly to the URL. This is the case for ChatGPT. The URL for ChatGPT is  https://chat.openai.com/chat . For other models or products for which you may create a reference, use the URL that links as directly as possible to the source (i.e., the page where you can access the model, not the publisher’s homepage).

What to include and what to exclude

Works included in a reference list.

The reference list provides a reliable way for readers to identify and locate the works cited in a paper. APA Style papers generally include reference lists, not  bibliographies.

In general, each work cited in the text must appear in the reference list, and each work in the reference list must be cited in the text. Check your work carefully before submitting your manuscript or course assignment to ensure no works cited in the text are missing from the reference list and vice versa, with only the following exceptions.

Works Excluded From a Reference List

There are a few kinds of works that are not included in a reference list. Usually a work is not included because readers cannot recover it or because the mention is so broad that readers do not need a reference list entry to understand the use.

Information on works included in a reference list is covered in Sections 2.12 and 8.4 of the  APA Publication Manual, Seventh Edition

*This guidance has been expanded from the 6th edition.*

• Personal communications  such as emails, phone calls, or text messages are cited in the text only, not in the reference list, because readers cannot retrieve personal communications.
• General mentions of whole websites, whole periodicals, and common software and apps in the text do not require in-text citations or reference list entries because the use is broad and the source is familiar.
• The source of an epigraph does not usually appear in the reference list unless the work is a scholarly book or journal. For example, if you open the paper with an inspirational quotation by a famous person, the source of the quotation does not appear in the reference list because the quotation is meant to set the stage for the work, not substantiate a key point.   
• Quotations from research participants in a study you conducted can be presented and discussed in the text but do not need citations or reference list entries. Citations and reference list entries are not necessary because the quotations are part of your original research. They could also compromise participants’ confidentiality, which is an ethical violation.
• References included in a meta-analysis, which are marked with an asterisk in the reference list, may be cited in the text (or not) at the author’s discretion. This exception is relevant only to authors who are conducting a meta-analysis.

DOIs and URLs

The DOI or URL is the final component of a reference list entry. Because so much scholarship is available and/or retrieved online, most reference list entries end with either a DOI or a URL.

• A DOI is a unique alphanumeric string that identifies content and provides a persistent link to its location on the internet. DOIs can be found in database records and the reference lists of published works.
• A URL specifies the location of digital information on the internet and can be found in the address bar of your internet browser. URLs in references should link directly to the cited work when possible.

Follow these guidelines for including DOIs and URLs in references:

• Include a DOI for all works that have a DOI, regardless of whether you used the online version or the print version.
• If a print work does not have a DOI, do not include any DOI or URL in the reference.
• If an online work has both a DOI and a URL, include only the DOI.
• For works without DOIs from websites (not including academic research databases), provide a URL in the reference (as long as the URL will work for readers).
• For works without DOIs from most  academic research databases , do not include a URL or database information in the reference because these works are widely available. The reference should be the same as the reference for a print version of the work.
• For works from databases that publish original, proprietary material available only in that database (such as the UpToDate database) or for works of limited circulation in databases (such as monographs in the ERIC database), include the name of the database or archive and the URL of the work. If the URL requires a login or is session-specific (meaning it will not resolve for readers), provide the URL of the database or archive home page or login page instead of the URL for the work. See the page on including  database information in references  for more information. 
• If the URL is no longer working or no longer provides readers access to the content you intend to cite, follow the guidance for works with  no source .
• Other alphanumeric identifiers such as the International Standard Book Number (ISBN) and the International Standard Serial Number (ISSN) are not included in APA Style references.

Follow these guidelines to format DOIs and URLs:

• Present both DOIs and URLs as hyperlinks (i.e., beginning with “http:” or “https:”).
• Because a hyperlink leads readers directly to the content, it is not necessary to include the words “Retrieved from” or “Accessed from” before a DOI or URL.
• It is acceptable to use either the default display settings for hyperlinks in your word-processing program (e.g., usually blue font, underlined) or plain text that is not underlined.
• Leave links live if the work is to be published or read online.
• Follow the current recommendations of the International DOI Foundation to format DOIs in the reference list, which as of this publication is as follows:

https://doi.org/ xxxxx

• The string “https://doi.org/” is a way of presenting a DOI as a link, and “xxxxx” refers to the DOI number.
• The preferred format of the DOI has changed over time. Although older works use previous formats (e.g., “http:/dx.doi.org/” or “doi:” or “DOI:” before the DOI number), in your reference list, standardize DOIs into the current preferred format for all entries. For example, use  https://doi.org/10.1037/a0040251  in your reference even though that article, published in 2016, presented the number in an older format.
• Copy and paste the DOI or URL from your web browser directly into your reference list to avoid transcription errors. Do not change the capitalization or punctuation of the DOI or URL. Do not add line breaks manually to the hyperlink; it is acceptable if your word-processing program automatically adds a break or moves the hyperlink to its own line.
• Do not add a period after the DOI or URL because this may interfere with link functionality.

When a DOI or URL is long or complex, you may use shortDOIs or shortened URLs if desired.

• Use the  shortDOI service  provided by the International DOI Foundation to create shortDOIs. A work can have only one DOI and only one shortDOI; the shortDOI service will either produce a new shortDOI for a work that has never had one or retrieve an existing shortDOI.
• Some websites provide their own branded shortened URLs, and independent URL shortening services are available as well. Any shortened URL is acceptable in a reference as long as you check the link to ensure that it takes you to the correct location.
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Citation styles: apa, mla, chicago, turabian, ieee.

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Quick Links

Listed below are a few quick links to resources that will aid you in citing sources.

• Sign up for a Mendeley, EndNote, or Zotero training class.
• APA 7th Edition Published in October 2019. Visit this page for links to resources and examples.
• MLA Need help with citing MLA style? Find information here along with links to books in PittCat and free online resources.
• Chicago/Turabian Need help with citing Chicago/Turabian style? Find examples here along with links to the online style manual and free online resources.

Getting Started: How to use this guide

This LibGuide was designed to provide you with assistance in citing your sources when writing an academic paper.

There are different styles which format the information differently. In each tab, you will find descriptions of each citation style featured in this guide along with links to online resources for citing and a few examples.

What is a citation and citation style?

A citation is a way of giving credit to individuals for their creative and intellectual works that you utilized to support your research. It can also be used to locate particular sources and combat plagiarism. Typically, a citation can include the author's name, date, location of the publishing company, journal title, or DOI (Digital Object Identifier).

A citation style dictates the information necessary for a citation and how the information is ordered, as well as punctuation and other formatting.

How to do I choose a citation style?

There are many different ways of citing resources from your research. The citation style sometimes depends on the academic discipline involved. For example:

• APA (American Psychological Association) is used by Education, Psychology, and Sciences
• MLA (Modern Language Association) style is used by the Humanities
• Chicago/Turabian style is generally used by Business, History, and the Fine Arts

*You will need to consult with your professor to determine what is required in your specific course.

Click the links below to find descriptions of each style along with a sample of major in-text and bibliographic citations, links to books in PittCat, online citation manuals, and other free online resources.

• APA Citation Style
• MLA Citation Style
• Chicago/Turabian Citation Style
• Tools for creating bibliographies (CItation Managers)

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How to Cite a Research Paper

Last Updated: March 29, 2024 Fact Checked

This article was reviewed by Gerald Posner and by wikiHow staff writer, Jennifer Mueller, JD . Gerald Posner is an Author & Journalist based in Miami, Florida. With over 35 years of experience, he specializes in investigative journalism, nonfiction books, and editorials. He holds a law degree from UC College of the Law, San Francisco, and a BA in Political Science from the University of California-Berkeley. He’s the author of thirteen books, including several New York Times bestsellers, the winner of the Florida Book Award for General Nonfiction, and has been a finalist for the Pulitzer Prize in History. He was also shortlisted for the Best Business Book of 2020 by the Society for Advancing Business Editing and Writing. There are 8 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 414,207 times.

When writing a paper for a research project, you may need to cite a research paper you used as a reference. The basic information included in your citation will be the same across all styles. However, the format in which that information is presented is somewhat different depending on whether you're using American Psychological Association (APA), Modern Language Association (MLA), Chicago, or American Medical Association (AMA) style.

Referencing a Research Paper

• In APA style, cite the paper: Last Name, First Initial. (Year). Title. Publisher.
• In Chicago style, cite the paper: Last Name, First Name. “Title.” Publisher, Year.
• In MLA style, cite the paper: Last Name, First Name. “Title.” Publisher. Year.

Citation Help

• For example: "Kringle, K., & Frost, J."

• For example: "Kringle, K., & Frost, J. (2012)."
• If the date, or any other information, are not available, use the guide at https://blog.apastyle.org/apastyle/2012/05/missing-pieces.html .

• For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer."
• If you found the research paper in a database maintained by a university, corporation, or other organization, include any index number assigned to the paper in parentheses after the title. For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. (Report No. 1234)."

• For example: "Kringle, K., & Frost, J. (2012). Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. (Report No. 1234). Retrieved from Alaska University Library Archives, December 24, 2017."

• For example: "(Kringle & Frost, 2012)."
• If there was no date on the research paper, use the abbreviation n.d. : "(Kringle & Frost, n.d.)."

• For example: "Kringle, Kris, and Jack Frost."

• For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis."

• For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis, Alaska University, 2012."

• For example: "Kringle, Kris, and Jack Frost. "Red Noses, Warm Hearts: The Glowing Phenomenon among North Pole Reindeer." Master's thesis, Alaska University, 2012. Accessed at https://www.northpolemedical.com/raising_rudolf."

• Footnotes are essentially the same as the full citation, although the first and last names of the authors aren't inverted.
• For parenthetical citations, Chicago uses the Author-Date format. For example: "(Kringle and Frost 2012)."

• For example: "Kringle, Kris, and Frost, Jack."

• For example: "Kringle, Kris, and Frost, Jack. "Red Noses, Warm Hearts: The Glowing Phenomenon Among North Pole Reindeer.""

• For example, suppose you found the paper in a collection of paper housed in university archives. Your citation might be: "Kringle, Kris, and Frost, Jack. "Red Noses, Warm Hearts: The Glowing Phenomenon Among North Pole Reindeer." Master's Theses 2000-2010. University of Alaska Library Archives. Accessed December 24, 2017."

• For example: "(Kringle & Frost, p. 33)."

• For example: "Kringle K, Frost J."

• For example: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer."

• For example: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. Nat Med. 2012; 18(9): 1429-1433."

• For example, if you're citing a paper presented at a conference, you'd write: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. Oral presentation at Arctic Health Association Annual Summit; December, 2017; Nome, Alaska."
• To cite a paper you read online, you'd write: "Kringle K, Frost J. Red noses, warm hearts: The glowing phenomenon among North Pole reindeer. https://www.northpolemedical.com/raising_rudolf"

• For example: "According to Kringle and Frost, these red noses indicate a subspecies of reindeer native to Alaska and Canada that have migrated to the North Pole and mingled with North Pole reindeer. 1 "

Community Q&A

• If you used a manual as a source in your research paper, you'll need to learn how to cite the manual also. Thanks Helpful 0 Not Helpful 0
• If you use any figures in your research paper, you'll also need to know the proper way to cite them in MLA, APA, AMA, or Chicago. Thanks Helpful 0 Not Helpful 0

You Might Also Like

• ↑ https://askus.library.wwu.edu/faq/116659
• ↑ https://guides.libraries.psu.edu/apaquickguide/intext
• ↑ https://owl.purdue.edu/owl/research_and_citation/chicago_manual_17th_edition/cmos_formatting_and_style_guide/general_format.html
• ↑ https://libanswers.snhu.edu/faq/48009
• ↑ https://www.chicagomanualofstyle.org/tools_citationguide/citation-guide-2.html
• ↑ https://owl.purdue.edu/owl/research_and_citation/mla_style/mla_formatting_and_style_guide/mla_in_text_citations_the_basics.html
• ↑ https://morningside.libguides.com/MLA8/location
• ↑ https://owl.purdue.edu/owl/research_and_citation/ama_style/index.html

About This Article

To cite a paper APA style, start with the author's last name and first initial, and the year of publication. Then, list the title of the paper, where you found it, and the date that you accessed it. In a paper, use a parenthetical reference with the last name of the author and the publication year. For an MLA citation, list the author's last name and then first name and the title of the paper in quotations. Include where you accessed the paper and the date you retrieved it. In your paper, use a parenthetical reference with the author's last name and the page number. Keep reading for tips on Chicago and AMA citations and exceptions to the citation rules! Did this summary help you? Yes No

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Citing Sources: Which citation style should I use?

The citation style you choose will largely be dictated by the discipline in which you're writing. For many assignments your instructor will suggest or require a certain style. If you're not sure which one to use, it's always best to check with your instructor or, if you are submitting a manuscript, the publisher to see if they require a certain style. In many cases, you may not be required to use any particular style as long as you pick one and use it consistently. If you have some flexibility, use the guide below to help you decide.

Disciplinary Citation Styles

• Social Sciences
• Sciences & Medicine
• Engineering

When in doubt, try: Chicago Notes

• Architecture & Landscape Architecture → try Chicago Notes or Chicago Author-Date
• Art → try Chicago Notes
• Art History → use  Chicago Notes
• Dance → try Chicago Notes or MLA
• Drama → try Chicago Notes or MLA
• Ethnomusicology → try Chicago Notes
• Music → try Chicago Notes
• Music History → use  Chicago Notes
• Urban Design & Planning → try Chicago Notes or Chicago Author-Date

When in doubt, try: MLA

• Cinema Studies → try MLA
• Classics → try Chicago Notes
• English → use  MLA
• History → use   Chicago Notes
• Linguistics → try MLA
• Languages → try MLA
• Literatures → use  MLA
• Philosophy → try MLA
• Religion → try Chicago Notes

When in doubt, try: APA or Chicago Notes

• Anthropology → try Chicago Author-Date
• Business → try APA (see also Citing Business Information from Foster Library)
• Communication → try APA
• Criminology & Criminal Justice → try Chicago Author-Date
• Economics → try APA
• Education → try APA
• Geography → try APA
• Government & Law (for non-law students) → try Chicago Notes
• History → try Chicago Notes
• Informatics → try APA
• Law (for law students) → use Bluebook
• Library & Information Science → try APA
• Museology → try Chicago Notes
• Political Science → try Chicago Notes
• Psychology → use  APA
• Social Work → try APA
• Sociology → use  ASA or Chicago Author-Date

When in doubt, try: CSE Name-Year or CSE Citation-Sequence

• Aquatic & Fisheries Sciences → try CSE Name-Year or APA
• Astronomy → try AIP or CSE Citation-Sequence
• Biology & Life Sciences → try CSE Name-Year or APA
• Chemistry → try ACS
• Earth & Space Sciences → try CSE Name-Year or APA
• Environmental Sciences → try CSE Name-Year or APA
• Forest Sciences → try CSE Name-Year or APA
• Health Sciences: Public Health, Medicine, & Nursing → use AMA or NLM
• Marine Sciences → try CSE Name-Year or APA
• Mathematics → try AMS or CSE Citation-Sequence
• Oceanography → try CSE Name-Year or APA
• Physics → try AIP or CSE Citation-Sequence
• Psychology  → use  APA

When in doubt, try: CSE Name-Year or IEEE

• Aeronautics and Astronautics → try CSE Citation-Sequence
• Bioengineering → try AMA or NLM
• Chemical Engineering → try ACS
• Civil and Environmental Engineering → try CSE Name-Year
• Computational Linguistics → try CSE Citation-Sequence
• Computer Science & Engineering → try IEEE
• Electrical and Computer Engineering → try IEEE
• Engineering (general) → try IEEE or CSE Name-Year
• Human Centered Design & Engineering → try IEEE
• Human-Computer Interaction + Design → try IEEE
• Industrial and Systems Engineering → try CSE Name-Yea r
• Mechanical Engineering → try Chicago Notes or Chicago Author-Date

See also: Additional Citation Styles , for styles used by specific engineering associations.

Pro Tip: Citation Tools Save Time & Stress!

If you’re enrolled in classes that each require a different citation style, it can get confusing really fast! The tools on the Quick Citation Generators section can help you format citations quickly in many different styles.

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Home / Guides / Citation Guides / APA Format

APA Format for Students & Researchers

In this guide, students and researchers can learn the basics of creating a properly formatted research paper according to APA guidelines.

It includes information on how to conceptualize, outline, and format the basic structure of your paper, as well as practical tips on spelling, abbreviation, punctuation, and more. The guide concludes with a complete sample paper as well as a final checklist that writers can use to prepare their work for submission.

APA Paper Formatting Basics

• All text should be double-spaced
• Use one-inch margins on all sides
• All paragraphs in the body are indented
• Make sure that the title is centered on the page with your name and school/institution underneath
• Use 12-point font throughout
• All pages should be numbered in the upper right hand corner
• The manual recommends using one space after most punctuation marks
• A shortened version of the title (“running head”) should be placed in the upper left hand corner

Table of Contents

Here’s a quick rundown of the contents of this guide on how to do APA format.

Information related to writing and organizing your paper:

• Paper and essay categories

General paper length

• Margin sizes
• Title pages
• Running Heads
• APA Outline
• APA Abstract
• The body of papers
• APA headings and subheadings
• Use of graphics (tables and figures)

Writing style tips:

Proper tone.

• Reducing bias and labels
• Abbreviation do’s and don’ts
• Punctuation
• Number rules

Citing Your Sources:

• Citing Sources
• In-text Citations
• Reference Page

Proofing Your Paper:

• Final checklist
• Submitting your project

APA Information:

• What is APA
• APA 7 Updates

What you won’t find in this guide: This guide provides information related to the formatting of your paper, as in guidelines related to spacing, margins, word choice, etc. While it provides a general overview of APA references, it does not provide instructions for how to cite in APA format.

For step-by-step instructions for citing books, journals, how to cite a website in APA format, information on an APA format bibliography, and more, refer to these other EasyBib guides:

• APA citation (general reference guide)
• APA In-text citation
• APA article citation
• APA book citation
• APA citation website

Or, you can use our automatic generator. Our APA formatter helps to build your references for you. Yep, you read that correctly.

Writing and Organizing Your APA Paper in an Effective Way

This section of our guide focuses on proper paper length, how to format headings, spacing, and more! This information can be found in Chapter 2 of the official manual (American Psychological Association, 2020, pp. 29-67).

Categories of papers

Before getting into the nitty-gritty details related to APA research paper format, first determine the type of paper you’re about to embark on creating:

Empirical studies

Empirical studies take data from observations and experiments to generate research reports. It is different from other types of studies in that it isn’t based on theories or ideas, but on actual data.

Literature reviews

These papers analyze another individual’s work or a group of works. The purpose is to gather information about a current issue or problem and to communicate where we are today. It sheds light on issues and attempts to fill those gaps with suggestions for future research and methods.

Theoretical articles

These papers are somewhat similar to a literature reviews in that the author collects, examines, and shares information about a current issue or problem, by using others’ research. It is different from literature reviews in that it attempts to explain or solve a problem by coming up with a new theory. This theory is justified with valid evidence.

Methodological articles

These articles showcase new advances, or modifications to an existing practice, in a scientific method or procedure. The author has data or documentation to prove that their new method, or improvement to a method, is valid. Plenty of evidence is included in this type of article. In addition, the author explains the current method being used in addition to their own findings, in order to allow the reader to understand and modify their own current practices.

Case studies

Case studies present information related an individual, group, or larger set of individuals. These subjects are analyzed for a specific reason and the author reports on the method and conclusions from their study. The author may also make suggestions for future research, create possible theories, and/or determine a solution to a problem.

Since APA style format is used often in science fields, the belief is “less is more.” Make sure you’re able to get your points across in a clear and brief way. Be direct, clear, and professional. Try not to add fluff and unnecessary details into your paper or writing.  This will keep the paper length shorter and more concise.

Margin sizes in APA Format

When it comes to margins, keep them consistent across the left, right, top, and bottom of the page. All four sides should be the same distance from the edge of the paper. It’s recommended to use at least one-inch margins around each side. It’s acceptable to use larger margins, but the margins should never be smaller than an inch.

Title pages in APA Format

The title page, or APA format cover page, is the first page of a paper or essay. Some teachers and professors do not require a title page, but some do. If you’re not sure if you should include one or not, ask your teacher. Some appreciate the page, which clearly displays the writer’s name and the title of the paper.

The APA format title page for student papers includes six main components:

• the title of the APA format paper
• names of all authors
• institutional affiliation
• course number and title
• instructor’s name

Title pages for professional papers  also require a running head; student papers do not.

Some instructors and professional publications also ask for an author’s note. If you’re required or would like to include an author’s note, place it below the institutional affiliation. Examples of information included in an author’s note include an ORCID iD number, a disclosure, and an acknowledgement.

Here are key guidelines to developing your title page:

• The title of the paper should capture the main idea of the essay, but should not contain abbreviations or words that serve no purpose. For example, instead of using the title “A Look at Amphibians From the Past,” title the paper “Amphibians From the Past.” Delete the unnecessary fluff!
• Center the title on the page and place it about 3-4 lines from the top.
• The title should be bolded, in title case, and the same font size as your other page text. Do not underline or italicize the title. Other text on the page should be plain (not bolded , underlined, or italicized ). 
• All text on the title page should be double-spaced. The APA format examples paper below displays proper spacing, so go take a look!
• Do not include any titles in the author’s name such as Dr. or Ms. In contrast, for your instructor’s name, use the form they prefer (e.g., Sagar Parekh, PhD; Dr. Minako Asato; Professor Nathan Ian Brown; etc.).
• The institutional affiliation is the school the author attends or the location where the author conducted the research.

In a hurry? Try the  EasyBib title page maker to easily create a title page for free.

Sample of an APA format title page for a student paper:

Sample of title page for a professional paper:

Running heads in APA Format

The 7th edition of the American Psychological Association Publication Manual (p. 37) states that running heads are not required for student papers unless requested by the instructor. Student papers still need a page number included in the upper right-hand corner of every page. The 6th edition required a running head for student papers, so be sure to confirm with your instructor which edition you should follow. Of note, this guide follows the 7th edition.

Running heads are required for professional papers (e.g., manuscripts submitted for publication). Read on for instructions on how to create them.

Are you wondering what is a “running head”? It’s basically a page header at the top of every page. To make this process easier, set your word processor to automatically add these components onto each page. You may want to look for “Header” in the features.

A running head/page header includes two pieces:

• the title of the paper
• page numbers.

Insert page numbers justified to the right-hand side of the APA format paper (do not put p. or pg. in front of the page numbers).

For all pages of the paper, including the APA format title page, include the “TITLE OF YOUR PAPER” justified to the left in capital letters (i.e., the running head). If your full title is long (over 50 characters), the running head title should be a shortened version.

Preparing outlines in APA Format

Outlines are extremely beneficial as they help writers stay organized, determine the scope of the research that needs to be included, and establish headings and subheadings.

There isn’t an official or recommended “APA format for outline” structure. It is up to the writer (if they choose to make use of an outline) to determine how to organize it and the characters to include. Some writers use a mix of roman numerals, numbers, and uppercase and lowercase letters.

Even though there isn’t a required or recommended APA format for an outline, we encourage writers to make use of one. Who wouldn’t want to put together a rough outline of their project? We promise you, an outline will help you stay on track.

Here’s our version of how APA format for outlines could look:

Don’t forget, if you’re looking for information on APA citation format and other related topics, check out our other comprehensive guides.

How to form an abstract in APA

An APA format abstract (p. 38) is a summary of a scholarly article or scientific study. Scholarly articles and studies are rather lengthy documents, and abstracts allow readers to first determine if they’d like to read an article in its entirety or not.

You may come across abstracts while researching a topic. Many databases display abstracts in the search results and often display them before showing the full text of an article or scientific study. It is important to create a high quality abstract that accurately communicates the purpose and goal of your paper, as readers will determine if it is worthy to continue reading or not.

Are you wondering if you need to create an abstract for your assignment? Usually, student papers do not require an abstract. Abstracts are not typically seen in class assignments, and are usually only included when submitting a paper for publication. Unless your teacher or professor asked for it, you probably don’t need to have one for your class assignment.

If you’re planning on submitting your paper to a journal for publication, first check the journal’s website to learn about abstract and APA paper format requirements.

Here are some helpful suggestions to create a dynamic abstract:

• Abstracts are found on their own page, directly after the title or cover page.
• Professional papers only (not student papers): Include the running head on the top of the page.
• On the first line of the page, center the word “Abstract” (but do not include quotation marks).
• On the following line, write a summary of the key points of your research. Your abstract summary is a way to introduce readers to your research topic, the questions that will be answered, the process you took, and any findings or conclusions you drew. Use concise, brief, informative language. You only have a few sentences to share the summary of your entire document, so be direct with your wording.
• This summary should not be indented, but should be double-spaced and less than 250 words.
• If applicable, help researchers find your work in databases by listing keywords from your paper after your summary. To do this, indent and type Keywords : in italics.  Then list your keywords that stand out in your research. You can also include keyword strings that you think readers will type into the search box.
• Active voice: The subjects reacted to the medication.
• Passive voice: There was a reaction from the subjects taking the medication.
• Instead of evaluating your project in the abstract, simply report what it contains.
• If a large portion of your work includes the extension of someone else’s research, share this in the abstract and include the author’s last name and the year their work was released.

APA format example page:

Here’s an example of an abstract:

Visual design is a critical aspect of any web page or user interface, and its impact on a user’s experience has been studied extensively. Research has shown a positive correlation between a user’s perceived usability and a user’s assessment of visual design. Additionally, perceived web quality, which encompasses visual design, has a positive relationship with both initial and continued consumer purchase intention. However, visual design is often assessed using self-report scale, which are vulnerable to a few pitfalls. Because self-report questionnaires are often reliant on introspection and honesty, it is difficult to confidently rely on self-report questionnaires to make important decisions. This study aims to ensure the validity of a visual design assessment instrument (Visual Aesthetics of Websites Inventory: Short version) by examining its relationship with biometric (variables), like galvanic skin response, pupillometry, and fixation information. Our study looked at participants assessment of a webpage’s visual design, and compared it to their biometric responses while viewing the webpage. Overall, we found that both average fixation duration and pupil dilation differed when participants viewed web pages with lower visual design ratings compared to web pages with a higher visual design rating.

Keywords : usability, visual design, websites, eye tracking, pupillometry, self-report, VisAWI

The body of an APA paper

On the page after the title page (if a student paper) or the abstract (if a professional paper), begin with the body of the paper.

Most papers follow this format:

• At the top of the page, add the page number in the upper right corner of all pages, including the title page.
• On the next line write the title in bold font and center it. Do not underline or italicize it.
• Begin with the introduction and indent the first line of the paragraph. All paragraphs in the body are indented.

Sample body for a student paper:

Most scientific or professional papers have additional sections and guidelines:

• Start with the running head (title + page number). The heading title should be in capital letters. The abstract page should be page 2.
• The introduction presents the problem and premise upon which the research was based. It goes into more detail about this problem than the abstract.
• Begin a new section with the Method and use this word as the subtitle. Bold and center this subtitle. The Method section shows how the study was run and conducted. Be sure to describe the methods through which data was collected.
• Begin a new section with the Results . Bold and center this subtitle. The Results section summarizes your data. Use charts and graphs to display this data.
• Draw conclusions and support how your data led to these conclusions.
• Discuss whether or not your hypothesis was confirmed or not supported by your results.
• Determine the limitations of the study and next steps to improve research for future studies.

Sample body for a professional paper:

Keep in mind, APA citation format is much easier than you think, thanks to EasyBib.com. Try our automatic generator and watch how we create APA citation format references for you in just a few clicks. While you’re at it, take a peek at our other helpful guides, such as our APA reference page guide, to make sure you’re on track with your research papers.

Proper usage of headings & subheadings in APA Format

Headings (p. 47) serve an important purpose in research papers — they organize your paper and make it simple to locate different pieces of information. In addition, headings provide readers with a glimpse to the main idea, or content, they are about to read.

In APA format, there are five levels of headings, each with a different formatting:

• This is the title of your paper
• The title should be centered in the middle of the page
• The title should be bolded
• Use uppercase and lowercase letters where necessary (called title capitalization)
• Place this heading against the left margin
• Use bold letters
• Use uppercase and lowercase letters where necessary
• Place this heading against the left side margin
• End the heading with a period
• Indented in from the left margin

Following general formatting rules, all headings are double spaced and there are no extra lines or spaces between sections.

Here is a visual APA format template for levels of headings:

Use of graphics (tables and figures) in APA Format

If you’re looking to jazz up your project with any charts, tables, drawings, or images, there are certain APA format rules (pp. 195-250) to follow.

First and foremost, the only reason why any graphics should be added is to provide the reader with an easier way to see or read information, rather than typing it all out in the text.

Lots of numbers to discuss? Try organizing your information into a chart or table. Pie charts, bar graphs, coordinate planes, and line graphs are just a few ways to show numerical data, relationships between numbers, and many other types of information.

Instead of typing out long, drawn out descriptions, create a drawing or image. Many visual learners would appreciate the ability to look at an image to make sense of information.

Before you go ahead and place that graphic in your paper, here are a few key guidelines:

• Follow them in the appropriate numerical order in which they appear in the text of your paper. Example : Figure 1, Figure 2, Table 1, Figure 3.
• Example: Figure 1, Figure 2, Table 1, Figure 3
• Only use graphics if they will supplement the material in your text. If they reinstate what you already have in your text, then it is not necessary to include a graphic.
• Include enough wording in the graphic so that the reader is able to understand its meaning, even if it is isolated from the corresponding text. However, do not go overboard with adding a ton of wording in your graphic.
• Left align tables and figures

In our APA format sample paper , you’ll find examples of tables after the references. You may also place tables and figures within the text just after it is mentioned.

Is there anything better than seeing a neatly organized data table? We think not! If you have tons of numbers or data to share, consider creating a table instead of typing out a wordy paragraph. Tables are pretty easy to whip up on Google Docs or Microsoft Word.

General format of a table should be:

• Table number
• Choose to type out your data OR create a table. As stated above, in APA format, you shouldn’t have the information typed out in your paper and also have a table showing the same exact information. Choose one or the other.
• If you choose to create a table, discuss it very briefly in the text. Say something along the lines of, “Table 1 displays the amount of money used towards fighting Malaria.” Or, “Stomach cancer rates are displayed in Table 4.”
• If you’re submitting your project for a class, place your table close to the text where it’s mentioned. If you’re submitting it to be published in a journal, most publishers prefer tables to be placed in the back. If you’re unsure where to place your tables, ask!
• Include the table number first and at the top. Table 1 is the first table discussed in the paper. Table 2 is the next table mentioned, and so on. This should be in bold.
• Add a title under the number. Create a brief, descriptive title. Capitalize the first letter for each important word. Italicize the title and place it under the table number.
• Only use horizontal lines.
• Limit use of cell shading.
• Keep the font at 12-point size and use single or double spacing. If you use single spacing in one table, make sure all of the others use single spaces as well. Keep it consistent.
• All headings should be centered.
• In the first column (called the stub), center the heading, left-align the information underneath it (indent 0.15 inches if info is more than one line).
• Information in other columns should be centered.
• General . Information about the whole table.
• Specific . Information targeted for a specific column, row, or cell.
• Probability . Explains what certain table symbols mean. For example, asterisks,  p values, etc.

Here’s an APA format example of a table:

We know putting together a table is pretty tricky. That’s why we’ve included not one, but a few tables on this page. Scroll down and look at the additional tables in the essay in APA format example found below.

Figures represent information in a visual way. They differ from tables in that they are visually appealing. Sure, tables, like the one above, can be visually appealing, but it’s the color, circles, arrows, boxes, or icons included that make a figure a “figure.”

There are many commonly used figures in papers. Examples APA Format:

• Photographs
• Hierarchy charts

General format of a figure is the same as tables. This means each should include:

• Figure number

Use the same formatting tables use for the number, title, and note.

Here are some pointers to keep in mind when it comes to APA format for figures:

• Only include a figure if it adds value to your paper. If it will truly help with understanding, include it!
• Either include a figure OR write it all out in the text. Do not include the same information twice.
• If a note is added, it should clearly explain the content of the figure. Include any reference information if it’s reproduced or adapted.

APA format sample of a figure:

Photographs:

We live in a world where we have tons of photographs available at our fingertips.

Photographs found through Google Images, social media, stock photos made available from subscription sites, and tons of other various online sources make obtaining photographs a breeze. We can even pull out our cell phones, and in just a few seconds, take pictures with our cameras.

Photographs are simple to find, and because of this, many students enjoy using them in their papers.

If you have a photograph you would like to include in your project, here are some guidelines from the American Psychological Association.

• Create a reference for the photograph. Follow the guidelines under the table and figure sections above.
• Do not use color photos. It is recommended to use black and white. Colors can change depending on the reader’s screen resolution. Using black and white ensures the reader will be able to view the image clearly. The only time it is recommended to use color photos is if you’re writing about color-specific things. For example, if you’re discussing the various shades of leaf coloration, you may want to include a few photographs of colorful leaves.
• If there are sections of the photograph that are not related to your work, it is acceptable to crop them out. Cropping is also beneficial in that it helps the reader focus on the main item you’re discussing.
• If you choose to include an image of a person you know, it would be respectful if you ask their permission before automatically including their photo in your paper.  Some schools and universities post research papers online and some people prefer that their photos and information stay off the Internet.

B. Writing Style Tips

Writing a paper for scientific topics is much different than writing for English, literature, and other composition classes. Science papers are much more direct, clear, and concise. This section includes key suggestions, explains how to write in APA format, and includes other tidbits to keep in mind while formulating your research paper.

Verb usage in APA

Research experiments and observations rely on the creation and analysis of data to test hypotheses and come to conclusions. While sharing and explaining the methods and results of studies, science writers often use verbs.

When using verbs in writing, make sure that you continue to use them in the same tense throughout the section you’re writing. Further details are in the publication manual (p. 117).

Here’s an APA format example:

We tested the solution to identify the possible contaminants.

It wouldn’t make sense to add this sentence after the one above:

We tested the solution to identify the possible contaminants. Researchers often test solutions by placing them under a microscope.

Notice that the first sentence is in the past tense while the second sentence is in the present tense. This can be confusing for readers.

For verbs in scientific papers, the APA manual recommends using:

• Past tense or present perfect tense for the explantation of the procedure
• Past tense for the explanation of the results
• Present tense for the explanation of the conclusion and future implications

If this is all a bit much, and you’re simply looking for help with your references, try the EasyBib.com APA format generator . Our APA formatter creates your references in just a few clicks. APA citation format is easier than you think thanks to our innovative, automatic tool.

Even though your writing will not have the same fluff and detail as other forms of writing, it should not be boring or dull to read. The Publication Manual suggests thinking about who will be the main reader of your work and to write in a way that educates them.

How to reduce bias & labels

The American Psychological Association strongly objects to any bias towards gender, racial groups, ages of individuals or subjects, disabilities, and sexual orientation (pp. 131-149). If you’re unsure whether your writing is free of bias and labels or not, have a few individuals read your work to determine if it’s acceptable.

Here are a few guidelines that the American Psychological Association suggests :

• Only include information about an individual’s orientation or characteristic if it is important to the topic or study. Do not include information about individuals or labels if it is not necessary.
• If writing about an individual’s characteristic or orientation, for essay APA format, make sure to put the person first. Instead of saying, “Diabetic patients,” say, “Patients who are diabetic.”
• Instead of using narrow terms such as, “adolescents,” or “the elderly,” try to use broader terms such as, “participants,” and “subjects.”
• “They” or “their” are acceptable gender-neutral pronouns to use.
• Be mindful when using terms that end with “man” or “men” if they involve subjects who are female. For example, instead of using “Firemen,” use the term, “Firefighter.” In general, avoid ambiguity.
• When referring to someone’s racial or ethnic identity, use the census category terms and capitalize the first letter. Also, avoid using the word, “minority,” as it can be interpreted as meaning less than or deficient. Instead, say “people of color” or “underrepresented groups.”
• When describing subjects in APA format, use the words “girls” and “boys” for children who are under the age of 12. The terms, “young woman,” “young man,” “female adolescent,” and “male adolescent” are appropriate for subjects between 13-17 years old; “Men,” and “women,” for those older than 18. Use the term, “older adults.” for individuals who are older. “Elderly,” and “senior,” are not acceptable if used only as nouns. It is acceptable to use these terms if they’re used as adjectives.

Read through our example essay in APA format, found in section D, to see how we’ve reduced bias and labels.

Spelling in APA Format

• In APA formatting, use the same spelling as words found in Merriam-Webster’s Collegiate Dictionary (American English) (p. 161).
• If the word you’re trying to spell is not found in Webster’s Collegiate Dictionary, a second resource is Webster’s Third New International Dictionary .
• If attempting to properly spell words in the psychology field, consult the American Psychological Association’s Dictionary of Psychology

Thanks to helpful tools and features, such as the spell checker, in word processing programs, most of us think we have everything we need right in our document. However, quite a few helpful features are found elsewhere.

Where can you find a full grammar editor? Right here, on EasyBib.com. The EasyBib Plus paper checker scans your paper for spelling, but also for any conjunction , determiner, or adverb out of place. Try it out and unlock the magic of an edited paper.

Abbreviation do’s and don’ts in APA Format

Abbreviations can be tricky. You may be asking yourself, “Do I include periods between the letters?” “Are all letters capitalized?” “Do I need to write out the full name each and every time?” Not to worry, we’re breaking down the publication manual’s abbreviations (p. 172) for you here.

First and foremost, use abbreviations sparingly.

Too many and you’re left with a paper littered with capital letters mashed together. Plus, they don’t lend themselves to smooth and easy reading. Readers need to pause and comprehend the meaning of abbreviations and quite often stumble over them.

• If the abbreviation is used less than three times in the paper, type it out each time. It would be pretty difficult to remember what an abbreviation or acronym stands for if you’re writing a lengthy paper.
• If you decide to sprinkle in abbreviations,  it is not necessary to include periods between the letters.
• Example: While it may not affect a patient’s short-term memory (STM), it may affect their ability to comprehend new terms. Patients who experience STM loss while using the medication should discuss it with their doctor.
• Example : AIDS
• The weight in pounds exceeded what we previously thought.

Punctuation in APA Format

One space after most punctuation marks.

The manual recommends using one space after most punctuation marks, including punctuation at the end of a sentence (p. 154). It doesn’t hurt to double check with your teacher or professor to ask their preference since this rule was changed recently (in 2020).

The official APA format book was primarily created to aid individuals with submitting their paper for publication in a professional journal. Many schools adopt certain parts of the handbook and modify sections to match their preference. To see an example of an APA format research paper, with the spacing we believe is most commonly and acceptable to use, scroll down and see section D.

For more information related to the handbook, including frequently asked questions, and more, here’s further reading on the style

It’s often a heated debate among writers whether or not to use an Oxford comma (p. 155), but for this style, always use an Oxford comma. This type of comma is placed before the words AND and OR or in a series of three items.

Example of APA format for commas: The medication caused drowsiness, upset stomach, and fatigue.

Here’s another example: The subjects chose between cold, room temperature, or warm water.

Apostrophes

When writing a possessive singular noun, you should place the apostrophe before the s. For possessive plural nouns, the apostrophe is placed after the s.

• Singular : Linda Morris’s jacket
• Plural : The Morris’ house

Em dashes (long dash) are used to bring focus to a particular point or an aside. There are no spaces after these dashes (p. 157).

Use en dashes (short dash) in compound adjectives. Do not place a space before or after the dash. Here are a few examples:

• custom-built
• 12-year-old

Number rules in APA Format

Science papers often include the use of numbers, usually displayed in data, tables, and experiment information. The golden rule to keep in mind is that numbers less than 10 are written out in text. If the number is more than 10, use numerals.

APA format examples:

• 14 kilograms
• seven individuals
• 83 years old
• Fourth grade

The golden rule for numbers has exceptions.

In APA formatting, use numerals if you are:

• Showing numbers in a table or graph
• 4 divided by 2
• 6-month-olds

Use numbers written out as words if you are:

• Ninety-two percent of teachers feel as though….
• Hundred Years’ War
• One-sixth of the students

Other APA formatting number rules to keep in mind:

• World War II
• Super Bowl LII
• It’s 1980s, not 1980’s!

Additional number rules can be found in the publication manual (p. 178)

Need help with other writing topics? Our plagiarism checker is a great resource for anyone looking for writing help. Say goodbye to an out of place noun , preposition , or adjective, and hello to a fully edited paper.

Overview of APA references

While writing a research paper, it is always important to give credit and cite your sources; this lets you acknowledge others’ ideas and research you’ve used in your own work. Not doing so can be considered plagiarism , possibly leading to a failed grade or loss of a job.

APA style is one of the most commonly used citation styles used to prevent plagiarism. Here’s more on crediting sources . Let’s get this statement out of the way before you become confused: An APA format reference and an APA format citation are two different things! We understand that many teachers and professors use the terms as if they’re synonyms, but according to this specific style, they are two separate things, with different purposes, and styled differently.

A reference displays all of the information about the source — the title, the author’s name, the year it was published, the URL, all of it! References are placed on the final page of a research project.

Here’s an example of a reference:

Wynne-Jones, T. (2015). The emperor of any place . Candlewick Press.

An APA format citation is an APA format in-text citation. These are found within your paper, anytime a quote or paraphrase is included. They usually only include the name of the author and the date the source was published.

Here’s an example of one:

Hypertrophic cardiomyopathy is even discussed in the book, The Emperor of Any Place . The main character, Evan, finds a mysterious diary on his father’s desk (the same desk his father died on, after suffering from a hypertrophic cardiomyopathy attack). Evan unlocks the truth to his father and grandfather’s past (Wynne-Jones, 2015).

Both of the ways to credit another individual’s work — in the text of a paper and also on the final page — are key to preventing plagiarism. A writer must use both types in a paper. If you cite something in the text, it must have a full reference on the final page of the project. Where there is one, there must be the other!

Now that you understand that, here’s some basic info regarding APA format references (pp. 281-309).

• Each reference is organized, or structured, differently. It all depends on the source type. A book reference is structured one way, an APA journal is structured a different way, a newspaper article is another way. Yes, it’s probably frustrating that not all references are created equal and set up the same way. MLA works cited pages are unique in that every source type is formatted the same way. Unfortunately, this style is quite different.
• Most references follow this general format:

Author’s Last name, First initial. Middle initial. (Year published). Title of source . URL.

Again, as stated in the above paragraph, you must look up the specific source type you’re using to find out the placement of the title, author’s name, year published, etc.

For more information on APA format for sources and how to reference specific types of sources, use the other guides on EasyBib.com. Here’s another useful site .

Looking for a full visual of a page of references? Scroll down and take a peek at our APA format essay example towards the bottom of this page. You’ll see a list of references and you can gain a sense of how they look.

Bonus: here’s a link to more about the fundamentals related to this particular style. If you want to brush up or catch up on the Modern Language Association’s style, here’s a great resource on how to cite websites in MLA .

In-text APA citation format

Did you find the perfect quote or piece of information to include in your project? Way to go! It’s always a nice feeling when we find that magical piece of data or info to include in our writing. You probably already know that you can’t just copy and paste it into your project, or type it in, without also providing credit to the original author.

Displaying where the original information came from is much easier than you think.Directly next to the quote or information you included, place the author’s name and the year nearby. This allows the reader of your work to see where the information originated.

APA allows for the use of two different forms of in-text citation, parenthetical and narrative Both forms of citation require two elements:

• author’s name
• year of publication

The only difference is the way that this information is presented to the reader.

Parenthetical citations are the more commonly seen form of in-text citations for academic work, in which both required reference elements are presented at the end of the sentence in parentheses. Example:

Harlem had many artists and musicians in the late 1920s (Belafonte, 2008).

Narrative citations allow the author to present one or both of the required reference elements inside of the running sentence, which prevents the text from being too repetitive or burdensome. When only one of the two reference elements is included in the sentence, the other is provided parenthetically. Example:

According to Belafonte (2008), Harlem was full of artists and musicians in the late 1920s.

If there are two authors listed in the source entry, then the parenthetical reference must list them both:

(Smith & Belafonte, 2008)

If there are three or more authors listed in the source entry, then the parenthetical reference can abbreviate with “et al.”, the latin abbreviation for “and others”:

(Smith et al., 2008)

The author’s names are structured differently if there is more than one author. Things will also look different if there isn’t an author at all (which is sometimes the case with website pages). For more information on APA citation format, check out this page on the topic: APA parenthetical citation and APA in-text citation . There is also more information in the official manual in chapter 8.

If it’s MLA in-text and parenthetical citations you’re looking for, we’ve got your covered there too! You might want to also check out his guide on parenthetical citing .

Would you benefit from having a tool that helps you easily generate citations that are in the text? Check out EasyBib Plus!

References page in APA Format

An APA format reference page is easier to create than you probably think. We go into detail on how to create this page on our APA reference page . We also have a guide for how to create an annotated bibliography in APA . But, if you’re simply looking for a brief overview of the reference page, we’ve got you covered here.

Here are some pointers to keep in mind when it comes to the references page in APA format:

• This VIP page has its very own page. Start on a fresh, clean document (p. 303).
• Center and bold the title “References” (do not include quotation marks, underline, or italicize this title).
• Alphabetize and double-space ALL entries.
• Use a readable font, such as Times New Roman, Arial, Calibri, or Lucida (p. 44).
• Every quote or piece of outside information included in the paper should be referenced and have an entry.
• Even though it’s called a “reference page,” it can be longer than one page. If your references flow onto the next page, then that’s a-okay.
• Only include the running head if it is required by your teacher or you’re writing a professional paper.

Sample reference page for a student paper:

Here’s another friendly reminder to use the EasyBib APA format generator (that comes with EasyBib Plus) to quickly and easily develop every single one of your references for you. Try it out! Our APA formatter is easy to use and ready to use 24/7.

Final APA Format Checklist

Prior to submitting your paper, check to make sure you have everything you need and everything in its place:

• Did you credit all of the information and quotes you used in the body of your paper and show a matching full reference at the end of the paper? Remember, you need both! Need more information on how to credit other authors and sources? Check out our other guides, or use the EasyBib APA format generator to credit your sources quickly and easily. EasyBib.com also has more styles than just the one this page focuses on.
• 12-pt. Times New Roman
• 11-pt. Calibri, Arial, Georgia
• 10-pt. Lucida, Sans Unicode, Computer Modern
• If you created an abstract, is it directly after the title page? Some teachers and professors do not require an abstract, so before you go ahead and include it, make sure it’s something he or she is expecting.
• Professional paper — Did you include a running head on every single page of your project?
• Student paper — Did you include page numbers in the upper right-hand corner of all your pages?
• Are all headings, as in section or chapter titles, properly formatted? If you’re not sure, check section number 9.
• Are all tables and figures aligned properly? Did you include notes and other important information directly below the table or figure? Include any information that will help the reader completely understand everything in the table or figure if it were to stand alone.
• Are abbreviations used sparingly? Did you format them properly?
• Is the entire document double spaced?
• Are all numbers formatted properly? Check section 17, which is APA writing format for numbers.
• Did you glance at the sample paper? Is your assignment structured similarly? Are all of the margins uniform?

Submitting Your APA Paper

Congratulations for making it this far! You’ve put a lot of effort into writing your paper and making sure the t’s are crossed and the i’s are dotted. If you’re planning to submit your paper for a school assignment, make sure you review your teacher or professor’s procedures.

If you’re submitting your paper to a journal, you probably need to include a cover letter.

Most cover letters ask you to include:

• The author’s contact information.
• A statement to the editor that the paper is original.
• If a similar paper exists elsewhere, notify the editor in the cover letter.

Once again, review the specific journal’s website for exact specifications for submission.

Okay, so you’re probably thinking you’re ready to hit send or print and submit your assignment. Can we offer one last suggestion? We promise it will only take a minute.

Consider running your paper through our handy dandy paper checker. It’s pretty simple.

Copy and paste or upload your paper into our checker. Within a minute, we’ll provide feedback on your spelling and grammar. If there’s a pronoun , interjection , or verb out of place, we’ll highlight it and offer suggestions for improvement. We’ll even take it a step further and point out any instances of possible plagiarism.

If it sounds too good to be true, then head on over to our innovative tool and give it a whirl. We promise you won’t be disappointed.

What is APA Format?

APA stands for the American Psychological Association . In this guide, you’ll find information related to “What is APA format?” in relation to writing and organizing your paper according to the American Psychological Association’s standards. Information on how to cite sources can be found on our APA citation page. The official American Psychological Association handbook was used as a reference for our guide and we’ve included page numbers from the manual throughout. However, this page is not associated with the association.

You’ll most likely use APA format if your paper is on a scientific topic. Many behavioral and social sciences use this organization’s standards and guidelines.

What are behavioral sciences? Behavioral sciences study human and animal behavior. They can include:

• Cognitive Science
• Neuroscience

What are social sciences? Social sciences focus on one specific aspect of human behavior, specifically social and cultural relationships. Social sciences can include:

• Anthropology
• Political Science
• Human Geography
• Archaeology
• Linguistics

What’s New in the 7th Edition?

This citation style was created by the American Psychological Association. Its rules and guidelines can be found in the Publication Manual of the American Psychological Association . The information provided in the guide above follows the 6th edition (2009) of the manual. The 7th edition was published in 2020 and is the most recent version.

The 7th edition of the Publication Manual is in full color and includes 12 sections (compared to 8 sections in the 6th edition). In general, this new edition differentiates between professional and student papers, includes guidance with accessibility in mind, provides new examples to follow, and has updated guidelines.We’ve selected a few notable updates below, but for a full view of all of the 7th edition changes visit the style’s website linked here .

• Paper title
• Student name
• Affiliation (e.g., school, department, etc.)
• Course number and title
• Course instructor
• 6th edition – Running head: SMARTPHONE EFFECTS ON ADOLESCENT SOCIALIZATION
• 7th edition – SMARTPHONE EFFECTS ON ADOLESCENT SOCIALIZATION
• Pronouns . “They” can be used as a gender-neutral pronoun.
• Bias-free language guidelines . There are updated and new sections on guidelines for this section. New sections address participation in research, socioeconomic status, and intersectionality.
• Spacing after sentences. Add only a single space after end punctuation.
• Tables and figures . The citing format is now streamlined so that both tables and figures should include a name and number above the table/figure, and a note underneath the table/figure.
• 6th ed. – (Ikemoto, Richardson, Murphy, Yoshida 2016)
• 7th ed. – (Ikemoto et al., 2016)
• Citing books. The location of the publisher can be omitted. Also, e-books no longer need to mention the format (e.g., Kindle, etc.)
• Example: https://doi.org/10.1038/s42255-019-0153-5
• Using URLs. URLs no longer need to be prefaced by the words “Retrieved from.”

New citing information . There is new guidance on citing classroom or intranet resources, and oral traditions or traditional knowledge of indigenous peoples.

Visit our EasyBib Twitter feed to discover more citing tips, fun grammar facts, and the latest product updates.

American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.) (2020). American Psychological Association. https://doi.org/10.1037/0000165-000

Published October 31, 2011. Updated May 14, 2020.

Written and edited by Michele Kirschenbaum and Elise Barbeau. Michele Kirschenbaum is a school library media specialist and the in-house librarian at EasyBib.com. Elise Barbeau is the Citation Specialist at Chegg. She has worked in digital marketing, libraries, and publishing.

APA Formatting Guide

APA Formatting

• Annotated Bibliography
• Block Quotes
• et al Usage
• Multiple Authors
• Paraphrasing
• Page Numbers
• Parenthetical Citations
• Sample Paper
• View APA Guide

Citation Examples

• Book Chapter
• Journal Article
• Magazine Article
• Newspaper Article
• Website (no author)
• View all APA Examples

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We should not use “et al.” in APA reference list entries. If the number of authors in the source is up to and including 20, list all author names and use an ampersand (&) before the final author’s name. If the number of authors is more than 20, list the first 19 authors’ names followed by an ellipsis (but no ampersand), and then add the final author’s name. An example of author names in a reference entry having more than 20 authors is given below:

Author Surname1, F. M., Author Surname2, F. M., Author Surname3, F. M., Author Surname4, F. M., Author Surname5, F. M., Author Surname6, F. M., Author Surname7, F. M., Author Surname8, F. M., Author Surname9, F. M., Author Surname10, F. M., Author Surname11, F. M., Author Surname12, F. M., Author Surname13, F. M., Author Surname14, F. M., Author Surname15, F. M., Author Surname16, F. M., Author Surname17, F. M., Author Surname18, F. M., Author Surname19, F. M., . . .  Last Author Surname, F. M. (Publication Year).

Alvarez, L. D., Peach, J. L., Rodriguez, J. F., Donald, L., Thomas, M., Aruck, A., Samy, K., Anthony, K., Ajey, M., Rodriguez, K. L., Katherine, K., Vincent, A., Pater, F., Somu, P., Pander, L., Berd, R., Fox, L., Anders, A., Kamala, W., . . . Nicole Jones, K. (2019).

Note that, unlike references with 2 to 20 author names, the symbol “&” is not used here before the last author’s name.

APA 7, released in October 2019, has some new updates. Here is a brief description of the updates made in APA 7.

Different types of papers and best practices are given in detail in Chapter 1.

How to format a student title page is explained in Chapter 2. Examples of a professional paper and a student paper are included.

Chapter 3 provides additional information on qualitative and mixed methods of research.

An update on writing style is included in Chapter 4.

In chapter 5, some best practices for writing with bias-free language are included.

Chapter 6 gives some updates on style elements including using a single space after a period, including a citation with an abbreviation, the treatment of numbers in abstracts, treatment for different types of lists, and the formatting of gene and protein names.

In Chapter 7, additional examples are given for tables and figures for different types of publications.

In Chapter 8, how to format quotations and how to paraphrase text are covered with additional examples. A simplified version of in-text citations is clearly illustrated.

Chapter 9 has many updates: listing all author names up to 20 authors, standardizing DOIs and URLs, and the formatting of an annotated bibliography.

Chapter 10 includes many examples with templates for all reference types. New rules covering the inclusion of the issue number for journals and the omission of publisher location from book references are provided. Explanations of how to cite YouTube videos, power point slides, and TED talks are included.

Chapter 11 includes many legal references for easy understanding.

Chapter 12 provides advice for authors on how to promote their papers.

For more information on some of the changes found in APA 7, check out this EasyBib article .

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How To Do In-Text Citations with Multiple Authors in APA Format

APA (or American Psychological Association) Style   was introduced in 1929 to establish a consistent style guide for scientific writing. It sought to make scientific works easier to read and understand. However, the style guidelines have expanded to include many disciplines, such as the humanities and health care.

The APA’s Publication Manual does not cover the general writing style rules in other editorial style guides, such as the MLA Handbook . APA Style seeks to create uniformity of common writing styles relevant to behavior and social sciences primarily.

Consistent formatting allows the reader to engage with the presented ideas rather than be distracted by the author’s personal formatting preferences. It also helps readers quickly review the document for references and sources to aid their research. Using APA Style keeps authors transparent by providing rules about citing their sources and giving credit for others’ ideas.

How to do in-text citations in APA

• Understanding “et. al.” usage in APA

Citing multiple authors in APA

• In-text citations for various author types in APA

Best practices and common mistakes

APA Style allows writers to credit and cite other works appropriately and avoid plagiarism through in-text citations. APA Style uses the author–date citation system, which requires notations to be included within the document to reference ideas, paraphrases and quotations from other bodies of work. Each in-text citation within the paper (or chart, footnote or figure) briefly identifies the cited work and guides the reader to a longer list of cited sources at the end of the document, called the reference list.

In-text citations can be written within a paper parenthetically or narratively. Both include the same information: the author’s last name and the publication date.

• Parenthetical citation : Great falls can be caused by sitting on tall walls (Dumpty, 1797).
• Narrative citation : Dumpty (1797) claims that great falls can be caused by sitting on tall walls.
• Reference list entry: Dumpty, Humpty (1797). Humpty Dumpty Sat on a Wall. Nursery Rhymes, 100.

APA Style requires citations to conform to a set of guidelines , which includes proper spelling of author names, consistency between the in-text citation information and its reference list entry and rules about crediting all facts and figures mentioned – especially those which are not common knowledge.

Understanding “et al.” usage in APA

Et al. is an abbreviation used to indicate multiple people. It’s the abbreviated version of “et alia,” a neutral plural version of “and others.” Most commonly, et al. indicates more than one contributor, such as multiple authors or editors, in a work.

In APA Style citations, et al. is used to indicate a cited work with three or more authors and serves as a way to condense the in-text citation to avoid confusion and unnecessary length. An APA in-text citation with three or more authors will include only the first author’s name plus “et al.” in every citation.

Citing multiple authors in APA Style is similar to MLA Style . For one or two authors, list the last name(s) followed by the year of publication. 

• One author: (Beyonce, 1997)
• Contributors: Daryl Hall and John Oates

To cite three or more authors using APA Style, use only the first author’s last name listed, plus “et al.” 

• Contributors: Earth, Wind and Fire

When two separate sources have the same abbreviated et al. form , spell out as many last names as needed to distinguish the sources from each other. It may include two last names followed by et al.

Similarly, when the first authors of separate sources share the same last name but have different initials, use their first initials in the in-text citations.

• Beyonce Knowles & Solange Knowles

In-text citation for various author types in APA

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• 29 April 2024

How reliable is this research? Tool flags papers discussed on PubPeer

• Dalmeet Singh Chawla

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RedacTek’s tool alerts users to PubPeer discussions, and indicates when a study, or the papers that it cites, has been retracted. Credit: deepblue4you/Getty

A free online tool released earlier this month alerts researchers if a paper cites studies that are mentioned on the website PubPeer , a forum scientists often use to raise integrity concerns surrounding published papers.

Studies are usually flagged on PubPeer when readers have suspicions, for example about image manipulation , plagiarism , data fabrication or artificial intelligence (AI)-generated text . PubPeer already offers its own browser plug-in that alerts users if a study that they are reading has been posted on the site. The new tool, a plug-in released on 13 April by RedacTek , based in Oakland, California, goes further — it searches through reference lists for papers that have been flagged. The software pulls information from many sources, including PubPeer’s database; data from the digital-infrastructure organization Crossref, which assigns digital object identifiers to articles; and OpenAlex , a free index of hundreds of millions of scientific documents.

It’s important to track mentions of referenced articles on PubPeer, says Jodi Schneider, an information scientist at the University of Illinois Urbana-Champaign, who has tried out the RedacTek plug-in. “Not every single reference that’s in the bibliography matters, but some of them do,” she adds. “When you see a large number of problems in somebody’s bibliography, that just calls everything into question.”

The aim of the tool is to flag potential problems with studies to researchers early on, to reduce the circulation of poor-quality science, says RedacTek founder Rick Meyler, who is based in Emeryville, California. Future versions might also use AI to automatically clarify whether the PubPeer comments on a paper are positive or negative, he adds.

Third-generation retractions

As well as flagging PubPeer discussions, the plug-in alerts users if a study, or a paper that it cites, has been retracted. There are existing tools that alert academics about retracted citations ; some can do this during the writing process, so that researchers are aware of the publication status of studies when constructing bibliographies. But with the new tool, users can opt in to receive notifications about further ‘generations’ of retractions — alerts cover not only the study that they are reading, but also the papers it cites, articles cited by those references and even papers cited by the secondary references.

The software also calculates a ‘retraction association value’ for studies, a metric that measures the extent to which the paper is associated with science that has been withdrawn from the literature. As well as informing individual researchers, the plug-in could help scholarly publishers to keep tabs on their own journals, Meyler says, because it allows users to filter by publication.

In its ‘paper scorecard’, the tool also flags any papers in the three generations of referenced studies in which more than 25% of papers in the bibliography are self-citations — references by authors to their previous works.

Future versions could highlight whether papers cited retracted studies before or after the retraction was issued, notes Meyler, or whether mentions of such studies acknowledge the retraction. That would be useful, says Schneider, who co-authored a 2020 analysis that found that as little as 4% of citations to retracted studies note that the referenced paper has been retracted 1 .

Meyler says that RedacTek is currently in talks with the scholarly-services firm Cabell’s International in Beaumont, Texas, which maintains pay-to-view lists of suspected predatory journals . These publish articles without running proper quality checks for issues such as plagiarism, but still collect authors’ fees. The plan is to use these lists to improve the tool so that it can also automatically flag any cited papers that are published in such journals.

Nature 629 , 271-272 (2024)

doi: https://doi.org/10.1038/d41586-024-01247-6

Schneider, J., Ye, D., Hill, A. M. & Whitehorn, A. S. Scientometrics 125 , 2877–2913 (2020).

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Abstract: Excellence in a wide variety of medical applications poses considerable challenges for AI, requiring advanced reasoning, access to up-to-date medical knowledge and understanding of complex multimodal data. Gemini models, with strong general capabilities in multimodal and long-context reasoning, offer exciting possibilities in medicine. Building on these core strengths of Gemini, we introduce Med-Gemini, a family of highly capable multimodal models that are specialized in medicine with the ability to seamlessly use web search, and that can be efficiently tailored to novel modalities using custom encoders. We evaluate Med-Gemini on 14 medical benchmarks, establishing new state-of-the-art (SoTA) performance on 10 of them, and surpass the GPT-4 model family on every benchmark where a direct comparison is viable, often by a wide margin. On the popular MedQA (USMLE) benchmark, our best-performing Med-Gemini model achieves SoTA performance of 91.1% accuracy, using a novel uncertainty-guided search strategy. On 7 multimodal benchmarks including NEJM Image Challenges and MMMU (health & medicine), Med-Gemini improves over GPT-4V by an average relative margin of 44.5%. We demonstrate the effectiveness of Med-Gemini's long-context capabilities through SoTA performance on a needle-in-a-haystack retrieval task from long de-identified health records and medical video question answering, surpassing prior bespoke methods using only in-context learning. Finally, Med-Gemini's performance suggests real-world utility by surpassing human experts on tasks such as medical text summarization, alongside demonstrations of promising potential for multimodal medical dialogue, medical research and education. Taken together, our results offer compelling evidence for Med-Gemini's potential, although further rigorous evaluation will be crucial before real-world deployment in this safety-critical domain.

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Volume 30, Number 7—July 2024

Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, United States, 2024

Suggested citation for this article

We report highly pathogenic avian influenza A(H5N1) virus in dairy cattle and cats in Kansas and Texas, United States, which reflects the continued spread of clade 2.3.4.4b viruses that entered the country in late 2021. Infected cattle experienced nonspecific illness, reduced feed intake and rumination, and an abrupt drop in milk production, but fatal systemic influenza infection developed in domestic cats fed raw (unpasteurized) colostrum and milk from affected cows. Cow-to-cow transmission appears to have occurred because infections were observed in cattle on Michigan, Idaho, and Ohio farms where avian influenza virus–infected cows were transported. Although the US Food and Drug Administration has indicated the commercial milk supply remains safe, the detection of influenza virus in unpasteurized bovine milk is a concern because of potential cross-species transmission. Continued surveillance of highly pathogenic avian influenza viruses in domestic production animals is needed to prevent cross-species and mammal-to-mammal transmission.

Highly pathogenic avian influenza (HPAI) viruses pose a threat to wild birds and poultry globally, and HPAI H5N1 viruses are of even greater concern because of their frequent spillover into mammals. In late 2021, the Eurasian strain of H5N1 (clade 2.3.4.4b) was detected in North America ( 1 , 2 ) and initiated an outbreak that continued into 2024. Spillover detections and deaths from this clade have been reported in both terrestrial and marine mammals in the United States ( 3 , 4 ). The detection of HPAI H5N1 clade 2.3.4.4b virus in severe cases of human disease in Ecuador ( 5 ) and Chile ( 6 ) raises further concerns regarding the pandemic potential of specific HPAI viruses.

In February 2024, veterinarians were alerted to a syndrome occurring in lactating dairy cattle in the panhandle region of northern Texas. Nonspecific illness accompanied by reduced feed intake and rumination and an abrupt drop in milk production developed in affected animals. The milk from most affected cows had a thickened, creamy yellow appearance similar to colostrum. On affected farms, incidence appeared to peak 4–6 days after the first animals were affected and then tapered off within 10–14 days; afterward, most animals were slowly returned to regular milking. Clinical signs were commonly reported in multiparous cows during middle to late lactation; ≈10%–15% illness and minimal death of cattle were observed on affected farms. Initial submissions of blood, urine, feces, milk, and nasal swab samples and postmortem tissues to regional diagnostic laboratories did not reveal a consistent, specific cause for reduced milk production. Milk cultures were often negative, and serum chemistry testing showed mildly increased aspartate aminotransferase, gamma-glutamyl transferase, creatinine kinase, and bilirubin values, whereas complete blood counts showed variable anemia and leukocytopenia.

In early March 2024, similar clinical cases were reported in dairy cattle in southwestern Kansas and northeastern New Mexico; deaths of wild birds and domestic cats were also observed within affected sites in the Texas panhandle. In > 1 dairy farms in Texas, deaths occurred in domestic cats fed raw colostrum and milk from sick cows that were in the hospital parlor. Antemortem clinical signs in affected cats were depressed mental state, stiff body movements, ataxia, blindness, circling, and copious oculonasal discharge. Neurologic exams of affected cats revealed the absence of menace reflexes and pupillary light responses with a weak blink response.

On March 21, 2024, milk, serum, and fresh and fixed tissue samples from cattle located in affected dairies in Texas and 2 deceased cats from an affected Texas dairy farm were received at the Iowa State University Veterinary Diagnostic Laboratory (ISUVDL; Ames, IA, USA). The next day, similar sets of samples were received from cattle located in affected dairies in Kansas. Milk and tissue samples from cattle and tissue samples from the cats tested positive for influenza A virus (IAV) by screening PCR, which was confirmed and characterized as HPAI H5N1 virus by the US Department of Agriculture National Veterinary Services Laboratory. Detection led to an initial press release by the US Department of Agriculture Animal and Plant Health Inspection Service on March 25, 2024, confirming HPAI virus in dairy cattle ( 7 ). We report the characterizations performed at the ISUVDL for HPAI H5N1 viruses infecting cattle and cats in Kansas and Texas.

Materials and Methods

Milk samples (cases 2–5) and fresh and formalin-fixed tissues (cases 1, 3–5) from dairy cattle were received at the ISUVDL from Texas on March 21 and from Kansas on March 22, 2024. The cattle exhibited nonspecific illness and reduced lactation, as described previously. The tissue samples for diagnostic testing came from 3 cows that were euthanized and 3 that died naturally; all postmortem examinations were performed on the premises of affected farms.

The bodies of 2 adult domestic shorthaired cats from a north Texas dairy farm were received at the ISUVDL for a complete postmortem examination on March 21, 2024. The cats were found dead with no apparent signs of injury and were from a resident population of ≈24 domestic cats that had been fed milk from sick cows. Clinical disease in cows on that farm was first noted on March 16; the cats became sick on March 17, and several cats died in a cluster during March 19–20. In total, >50% of the cats at that dairy became ill and died. We collected cerebrum, cerebellum, eye, lung, heart, spleen, liver, lymph node, and kidney tissue samples from the cats and placed them in 10% neutral-buffered formalin for histopathology.

At ISUVDL, we trimmed, embedded in paraffin, and processed formalin-fixed tissues from affected cattle and cats for hematoxylin/eosin staining and histologic evaluation. For immunohistochemistry (IHC), we prepared 4-µm–thick sections from paraffin-embedded tissues, placed them on Superfrost Plus slides (VWR, https://www.vwr.com ), and dried them for 20 minutes at 60°C. We used a Ventana Discovery Ultra IHC/ISH research platform (Roche, https://www.roche.com ) for deparaffinization until and including counterstaining. We obtained all products except the primary antibody from Roche. Automated deparaffination was followed by enzymatic digestion with protease 1 for 8 minutes at 37°C and endogenous peroxidase blocking. We obtained the primary influenza A virus antibody from the hybridoma cell line H16-L10–4R5 (ATCC, https://www.atcc.org ) and diluted at 1:100 in Discovery PSS diluent; we incubated sections with antibody for 32 minutes at room temperature. Next, we incubated the sections with a hapten-labeled conjugate, Discovery anti-mouse HQ, for 16 minutes at 37°C followed by a 16-minute incubation with the horse radish peroxidase conjugate, Discovery anti-HQ HRP. We used a ChromoMap DAB kit for antigen visualization, followed by counterstaining with hematoxylin and then bluing. Positive controls were sections of IAV-positive swine lung. Negative controls were sections of brain, lung, and eyes from cats not infected with IAV.

We diluted milk samples 1:3 vol/vol in phosphate buffered saline, pH 7.4 (Gibco/Thermo Fisher Scientific, https://www.thermofisher.com ) by mixing 1 unit volume of milk and 3 unit volumes of phosphate buffered saline. We prepared 10% homogenates of mammary glands, brains, lungs, spleens, and lymph nodes in Earle’s balanced salt solution (Sigma-Aldrich, https://www.sigmaaldrich.com ). Processing was not necessary for ocular fluid, rumen content, or serum samples. After processing, we extracted samples according to a National Animal Health Laboratory Network (NAHLN) protocol that had 2 NAHLN-approved deviations for ISUVDL consisting of the MagMax Viral RNA Isolation Kit for 100 µL sample volumes and a Kingfisher Flex instrument (both Thermo Fisher Scientific).

We performed real-time reverse transcription PCR (rRT-PCR) by using an NAHLN-approved assay with 1 deviation, which was the VetMAX-Gold SIV Detection kit (Thermo Fisher Scientific), to screen for the presence of IAV RNA. We tested samples along with the VetMAX XENO Internal Positive Control to monitor the possible presence of PCR inhibitors. Each rRT-PCR 96-well plate had 2 positive amplification controls, 2 negative amplification controls, 1 positive extraction control, and 1 negative extraction control. We ran the rRT-PCR on an ABI 7500 Fast thermocycler and analyzed data with Design and Analysis Software 2.7.0 (both Thermo Fisher Scientific). We considered samples with cycle threshold (Ct) values <40.0 to be positive for virus.

After the screening rRT-PCR, we analyzed IAV RNA–positive samples for the H5 subtype and H5 clade 2.3.4.4b by using the same RNA extraction and NAHLN-approved rRT-PCR protocols as described previously, according to standard operating procedures. We performed PCR on the ABI 7500 Fast thermocycler by using appropriate controls to detect H5-specific IAV. We considered samples with Ct values <40.0 to be positive for the IAV H5 subtype.

We conducted genomic sequencing of 2 milk samples from infected dairy cattle from Texas and 2 tissue samples (lung and brain) from cats that died at a different Texas dairy. We subjected the whole-genome sequencing data to bioinformatics analysis to assemble the 8 different IAV segment sequences according to previously described methods ( 8 ). We used the hemagglutinin (HA) and neuraminidase (NA) sequences for phylogenetic analysis. We obtained reference sequences for the HA and NA segments of IAV H5 clade 2.3.4.4 from publicly available databases, including GISAID ( https://www.gisaid.org ) and GenBank. We aligned the sequences by using MAFFT version 7.520 software ( https://mafft.cbrc.jp/alignment/server/index.html ) to create multiple sequence alignments for subsequent phylogenetic analysis. We used IQTree2 ( https://github.com/iqtree/iqtree2 ) to construct the phylogenetic tree from the aligned sequences. The software was configured to automatically identify the optimal substitution model by using the ModelFinder Plus option, ensuring the selection of the most suitable model for the dataset and, thereby, improving the accuracy of the reconstructed tree. We visualized the resulting phylogenetic tree by using iTOL ( https://itol.embl.de ), a web-based platform for interactive tree exploration and annotation.

Gross Lesions in Cows and Cats

All cows were in good body condition with adequate rumen fill and no external indications of disease. Postmortem examinations of the affected dairy cows revealed firm mammary glands typical of mastitis; however, mammary gland lesions were not consistent. Two cows that were acutely ill before postmortem examination had grossly normal milk and no abnormal mammary gland lesions. The gastrointestinal tract of some cows had small abomasal ulcers and shallow linear erosions of the intestines, but those observations were also not consistent in all animals. The colon contents were brown and sticky, suggesting moderate dehydration. The feces contained feed particles that appeared to have undergone minimal ruminal fermentation. The rumen contents had normal color and appearance but appeared to have undergone minimal fermentation.

The 2 adult cats (1 intact male, 1 intact female) received at the ISUVDL were in adequate body and postmortem condition. External examination was unremarkable. Mild hemorrhages were observed in the subcutaneous tissues over the dorsal skull, and multifocal meningeal hemorrhages were observed in the cerebrums of both cats. The gastrointestinal tracts were empty, and no other gross lesions were observed.

Microscopic Lesions in Cows and Cats

Figure 1 . Mammary gland lesions in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. A, B) Mammary gland...

The chief microscopic lesion observed in affected cows was moderate acute multifocal neutrophilic mastitis ( Figure 1 ); however, mammary glands were not received from every cow. Three cows had mild neutrophilic or lymphocytic hepatitis. Because they were adult cattle, other observed microscopic lesions (e.g., mild lymphoplasmacytic interstitial nephritis and mild to moderate lymphocytic abomasitis) were presumed to be nonspecific, age-related changes. We did not observe major lesions in the other evaluated tissues. We performed IHC for IAV antigen on all evaluated tissues; the only tissues with positive immunoreactivity were mastitic mammary glands from 2 cows that showed nuclear and cytoplasmic labeling of alveolar epithelial cells and cells within lumina ( Figure 1 ) and multifocal germinal centers within a lymph node from 1 cow ( Table 1 ).

Figure 2 . Lesions in cat tissues in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Tissue sections were stained with...

Both cats had microscopic lesions consistent with severe systemic virus infection, including severe subacute multifocal necrotizing and lymphocytic meningoencephalitis with vasculitis and neuronal necrosis, moderate subacute multifocal necrotizing and lymphocytic interstitial pneumonia, moderate to severe subacute multifocal necrotizing and lymphohistiocytic myocarditis, and moderate subacute multifocal lymphoplasmacytic chorioretinitis with ganglion cell necrosis and attenuation of the internal plexiform and nuclear layers ( Table 2 ; Figure 2 ). We performed IHC for IAV antigen on multiple tissues (brain, eye, lung, heart, spleen, liver, and kidney). We detected positive IAV immunoreactivity in brain (intracytoplasmic, intranuclear, and axonal immunolabeling of neurons), lung, and heart, and multifocal and segmental immunoreactivity within all layers of the retina ( Figure 2 ).

PCR Data from Cows and Cats

We tested various samples from 8 clinically affected mature dairy cows by IAV screening and H5 subtype-specific PCR ( Table 3 ). Milk and mammary gland homogenates consistently showed low Ct values: 12.3–16.9 by IAV screening PCR, 17.6–23.1 by H5 subtype PCR, and 14.7–20.0 by H5 2.3.4.4 clade PCR (case 1, cow 1; case 2, cows 1 and 2; case 3, cow 1; and case 4, cow 1). We forwarded the samples to the National Veterinary Services Laboratory, which confirmed the virus was an HPAI H5N1 virus strain.

When available, we also tested tissue homogenates (e.g., lung, spleen, and lymph nodes), ocular fluid, and rumen contents from 6 cows by IAV and H5 subtype-specific PCR ( Table 3 ). However, the PCR findings were not consistent. For example, the tissue homogenates and ocular fluid tested positive in some but not all cows. In case 5, cow 1, the milk sample tested negative by IAV screening PCR, but the spleen homogenate tested positive by IAV screening, H5 subtype, and H5 2.3.4.4 PCR. For 2 cows (case 3, cow 1; and case 4, cow 1) that had both milk and rumen contents available, both samples tested positive for IAV. Nevertheless, all IAV-positive nonmammary gland tissue homogenates, ocular fluid, and rumen contents had markedly elevated Ct values in contrast to the low Ct values for milk and mammary gland homogenate samples.

We tested brain and lung samples from the 2 cats (case 6, cats 1 and 2) by IAV screening and H5 subtype-specific PCR ( Table 3 ). Both sample types were positive by IAV screening PCR; Ct values were 9.9–13.5 for brain and 17.4–24.4 for lung samples, indicating high amounts of virus nucleic acid in those samples. The H5 subtype and H5 2.3.4.4 PCR results were also positive for the brain and lung samples; Ct values were consistent with the IAV screening PCR ( Table 3 ).

Phylogenetic Analyses

We assembled the sequences of all 8 segments of the HPAI viruses from both cow milk and cat tissue samples. We used the hemagglutinin (HA) and neuraminidase (NA) sequences specifically for phylogenetic analysis to delineate the clade of the HA gene and subtype of the NA gene.

Figure 3 . Phylogenetic analysis of hemagglutinin gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different...

For HA gene analysis, both HA sequences derived from cow milk samples exhibited a high degree of similarity, sharing 99.88% nucleotide identity, whereas the 2 HA sequences from cat tissue samples showed complete identity at 100%. The HA sequences from the milk samples had 99.94% nucleotide identities with HA sequences from the cat tissues, resulting in a distinct subcluster comprising all 4 HA sequences, which clustered together with other H5N1 viruses belonging to clade 2.3.4.4b ( Figure 3 ). The HA sequences were deposited in GenBank (accession nos. PP599465 [case 2, cow 1], PP599473 [case 2, cow 2], PP692142 [case 6, cat 1], and PP692195 [case 6, cat 2]).

Figure 4 . Phylogenetic analysis of neuraminidase gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate different...

For NA gene analysis, the 2 NA sequences obtained from cow milk samples showed 99.93% nucleotide identity. Moreover, the NA sequences derived from the milk samples exhibited complete nucleotide identities (100%) with those from the cat tissues. The 4 NA sequences were grouped within the N1 subtype of HPAI viruses ( Figure 4 ). The NA sequences were deposited in GenBank (accession nos. PP599467 [case 2, cow 1], PP599475 [case 2, cow 2], PP692144 [case 6, cat 1], and PP692197 [case 6, cat 2]).

This case series differs from most previous reports of IAV infection in bovids, which indicated cattle were inapparently infected or resistant to infection ( 9 ). We describe an H5N1 strain of IAV in dairy cattle that resulted in apparent systemic illness, reduced milk production, and abundant virus shedding in milk. The magnitude of this finding is further emphasized by the high death rate (≈50%) of cats on farm premises that were fed raw colostrum and milk from affected cows; clinical disease and lesions developed that were consistent with previous reports of H5N1 infection in cats presumably derived from consuming infected wild birds ( 10 – 12 ). Although exposure to and consumption of dead wild birds cannot be completely ruled out for the cats described in this report, the known consumption of unpasteurized milk and colostrum from infected cows and the high amount of virus nucleic acid within the milk make milk and colostrum consumption a likely route of exposure. Therefore, our findings suggest cross-species mammal-to-mammal transmission of HPAI H5N1 virus and raise new concerns regarding the potential for virus spread within mammal populations. Horizontal transmission of HPAI H5N1 virus has been previously demonstrated in experimentally infected cats ( 13 ) and ferrets ( 14 ) and is suspected to account for large dieoffs observed during natural outbreaks in mink ( 15 ) and sea lions ( 16 ). Future experimental studies of HPAI H5N1 virus in dairy cattle should seek to confirm cross-species transmission to cats and potentially other mammals.

Clinical IAV infection in cattle has been infrequently reported in the published literature. The first report occurred in Japan in 1949, where a short course of disease with pyrexia, anorexia, nasal discharge, pneumonia, and decreased lactation developed in cattle ( 17 ). In 1997, a similar condition occurred in dairy cows in southwest England leading to a sporadic drop in milk production ( 18 ), and IAV seroconversion was later associated with reduced milk yield and respiratory disease ( 19 – 21 ). Rising antibody titers against human-origin influenza A viruses (H1N1 and H3N2) were later again reported in dairy cattle in England, which led to an acute fall in milk production during October 2005–March 2006 ( 22 ). Limited reports of IAV isolation from cattle exist; most reports occurred during the 1960s and 1970s in Hungary and in the former Soviet Union, where H3N2 was recovered from cattle experiencing respiratory disease ( 9 , 23 ). Direct detection of IAV in milk and the potential transmission from cattle to cats through feeding of unpasteurized milk has not been previously reported.

An IAV-associated drop in milk production in dairy cattle appears to have occurred during > 4 distinct periods and within 3 widely separated geographic areas: 1949 in Japan ( 17 ), 1997–1998 and 2005–2006 in Europe ( 19 , 21 ), and 2024 in the United States (this report). The sporadic occurrence of clinical disease in dairy cattle worldwide might be the result of changes in subclinical infection rates and the presence or absence of sufficient baseline IAV antibodies in cattle to prevent infection. Milk IgG, lactoferrin, and conglutinin have also been suggested as host factors that might reduce susceptibility of bovids to IAV infection ( 9 ). Contemporary estimates of the seroprevalence of IAV antibodies in US cattle are not well described in the published literature. One retrospective serologic survey in the United States in the late 1990s showed 27% of serum samples had positive antibody titers and 31% had low-positive titers for IAV H1 subtype-specific antigen in cattle with no evidence of clinical infections ( 24 ). Antibody titers for H5 subtype-specific antigen have not been reported in US cattle.

The susceptibility of domestic cats to HPAI H5N1 is well-documented globally ( 10 – 12 , 25 – 28 ), and infection often results in neurologic signs in affected felids and other terrestrial mammals ( 4 ). Most cases in cats result from consuming infected wild birds or contaminated poultry products ( 12 , 27 ). The incubation period in cats is short; clinical disease is often observed 2–3 days after infection ( 28 ). Brain tissue has been suggested as the best diagnostic sample to confirm HPAI virus infection in cats ( 10 ), and our results support that finding. One unique finding in the cats from this report is the presence of blindness and microscopic lesions of chorioretinitis. Those results suggest that further investigation into potential ocular manifestations of HPAI H5N1 virus infection in cats might be warranted.

The genomic sequencing and subsequent analysis of clinical samples from both bovine and feline sources provided considerable insights. The HA and NA sequences derived from both bovine milk and cat tissue samples from different Texas farms had a notable degree of similarity. Those findings strongly suggest a shared origin for the viruses detected in the dairy cattle and cat tissues. Further research, case series investigations, and surveillance data are needed to better understand and inform measures to curtail the clinical effects, shedding, and spread of HPAI viruses among mammals. Although pasteurization of commercial milk mitigates risks for transmission to humans, a 2019 US consumer study showed that 4.4% of adults consumed raw milk > 1 time during the previous year ( 29 ), indicating a need for public awareness of the potential presence of HPAI H5N1 viruses in raw milk.

Ingestion of feed contaminated with feces from wild birds infected with HPAI virus is presumed to be the most likely initial source of infection in the dairy farms. Although the exact source of the virus is unknown, migratory birds (Anseriformes and Charadriiformes) are likely sources because the Texas panhandle region lies in the Central Flyway, and those birds are the main natural reservoir for avian influenza viruses ( 30 ). HPAI H5N1 viruses are well adapted to domestic ducks and geese, and ducks appear to be a major reservoir ( 31 ); however, terns have also emerged as an important source of virus spread ( 32 ). The mode of transmission among infected cattle is also unknown; however, horizontal transmission has been suggested because disease developed in resident cattle herds in Michigan, Idaho, and Ohio farms that received infected cattle from the affected regions, and those cattle tested positive for HPAI H5N1 ( 33 ). Experimental studies are needed to decipher the transmission routes and pathogenesis (e.g., replication sites and movement) of the virus within infected cattle.

In conclusion, we showed that dairy cattle are susceptible to infection with HPAI H5N1 virus and can shed virus in milk and, therefore, might potentially transmit infection to other mammals via unpasteurized milk. A reduction in milk production and vague systemic illness were the most commonly reported clinical signs in affected cows, but neurologic signs and death rapidly developed in affected domestic cats. HPAI virus infection should be considered in dairy cattle when an unexpected and unexplained abrupt drop in feed intake and milk production occurs and for cats when rapid onset of neurologic signs and blindness develop. The recurring nature of global HPAI H5N1 virus outbreaks and detection of spillover events in a broad host range is concerning and suggests increasing virus adaptation in mammals. Surveillance of HPAI viruses in domestic production animals, including cattle, is needed to elucidate influenza virus evolution and ecology and prevent cross-species transmission.

Dr. Burrough is a professor and diagnostic pathologist at the Iowa State University College of Veterinary Medicine and Veterinary Diagnostic Laboratory. His research focuses on infectious diseases of livestock with an emphasis on swine.

Acknowledgment

We thank the faculty and staff at the ISUVDL who contributed to the processing and analysis of clinical samples in this investigation, the veterinarians involved with clinical assessments at affected dairies and various conference calls in the days before diagnostic submissions that ultimately led to the detection of HPAI virus in the cattle, and the US Department of Agriculture National Veterinary Services Laboratory and NAHLN for their roles and assistance in providing their expertise, confirmatory diagnostic support, and communications surrounding the HPAI virus cases impacting lactating dairy cattle.

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• Figure 1 . Mammary gland lesions in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. A, B) Mammary...
• Figure 2 . Lesions in cat tissues in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Tissue sections were stained...
• Figure 3 . Phylogenetic analysis of hemagglutinin gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate...
• Figure 4 . Phylogenetic analysis of neuraminidase gene sequences in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Colors indicate...
• Table 1 . Microscopic lesions observed in cattle in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024
• Table 2 . Microscopic lesions observed in cats in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024
• Table 3 . PCR results from various specimens in study of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024

Suggested citation for this article : Burrough ER, Magstadt DR, Petersen B, Timmermans SJ, Gauger PC, Zhang J, et al. Highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infection in domestic dairy cattle and cats, United States, 2024. Emerg Infect Dis. 2024 Jul [ date cited ]. https://doi.org/10.3201/eid3007.240508

DOI: 10.3201/eid3007.240508

Original Publication Date: April 29, 2024

Table of Contents – Volume 30, Number 7—July 2024

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Eric R. Burrough, Iowa State University Veterinary Diagnostic Laboratory, 1937 Christensen Dr, Ames, IA 50011, USA

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