How to Cite an Encyclopedia Article in AMA Style (11th Ed.)

To cite an encyclopedia article in AMA style (11th edition), use the book-chapter pattern: entry author, entry title in sentence case, "In:", the editors followed by "eds.", the encyclopedia title in italics, the volume and edition if they apply, then the publisher, year and page range. Online entries end with "Accessed" plus the date and the URL. In your text, the entry gets a superscript number like any other AMA source.

Author AA. Title of entry. In: Editor AA, Editor BB, eds. Title of Encyclopedia. Vol no. Nth ed. Publisher; Year:pages. Accessed Month DD, YYYY. URL

The same pattern covers medical dictionaries and pharmacopoeias. With small changes it also covers the point-of-care references nursing, pharmacy and medical students actually use: StatPearls, UpToDate, DynaMed, Micromedex and Lexidrug. Each of those is below with an example taken from a university library's AMA 11 guide, along with the cases where the manual gives no direct answer.

The AMA 11 rule for encyclopedia entries

The AMA Manual of Style has no separate template for encyclopedias. James Cook University Library's AMA 11th referencing guide says the format for an entry from "a pharmacopoeia, encyclopaedia, medical dictionary, or similar reference work" is "the same pattern used for a book chapter." That ties it to the manual's chapter rule, section 3.12.4 (Reference to a chapter in a book), and for online versions to section 3.12.11 on electronic books.

So an encyclopedia entry is a chapter, and the encyclopedia is the book it sits in. Here are the elements in order:

Three things in that table changed from the 10th edition, and older guides still show the old forms. The AMA Style Insider's preview of the 11th edition announced "the omission of publisher locations from references to books and reports" and said the new edition "will put URLs at the end of a reference, similar to how DOIs currently appear." In practice:

• A reference that reads Springfield, MA: Merriam-Webster Inc; 2004 follows the 10th edition. In AMA 11 it becomes Merriam-Webster Inc; 2004.
• The URL is the last element, and nothing follows it.
• No period goes after the URL or the DOI, so the link still works when someone copies it.

Authors. For one to six authors, list all of them. For seven or more, list the first three and then "et al," following the University of Southern California's AMA 11 reference list guide. Editors of the reference work follow the same rule and take "ed." or "eds." after the last name.

Worked examples

Each example below comes from a published AMA 11 library guide and keeps that guide's punctuation. Wherever an example ends in "URL," the guide uses that as a placeholder, and you put the full address of the page you read in its place.

1. A dictionary or encyclopedia entry with named editors

From the JCU guide, a veterinary dictionary read online:

Antihistamines. In: Andrews A, Boden E, eds. Black's Veterinary Dictionary. Bloomsbury; 2015. Accessed July 20, 2015. URL

The entry has no named author, so the reference opens with the entry title. The editors stay after "In:", where they belong to the book. Black's Veterinary Dictionary goes in italics in your paper.

2. A print pharmacopoeia with a volume and an edition

Carbamazepine tablets. In: The Pharmacopoeia of the United States of America. Vol 2. 31st ed. The United States Pharmacopeial Convention; 2007:1631.

The volume comes before the edition, and the page number follows the year after a colon with no space. A single page is fine when the entry fits on one.

3. A dated pharmacopoeia edition with a page range

Ceylon cinnamon bark oil. In: British Pharmacopoeia 2013. Vol 5. The Stationery Office; 2012:3659-3660.

The year in the title (2013) and the publication year (2012) differ, and both stay. The title year is part of the title. The second year is when the book was published.

4. A StatPearls chapter

StatPearls appears on the NCBI Bookshelf, and students cite it more than almost anything else in clinical coursework. South College Library's AMA 11 database page gives the pattern as "Author InIn. Title of chapter in sentence case. In: Book Title in Italics. Publisher Name. Updated [Date]. Accessed [Date]." and this example:

Shamrock AG, Dreyer MA, Varacallo M. Achilles tendon rupture. In: StatPearls [Internet]. StatPearls Publishing. Updated August 17, 2023. Accessed October 24, 2024. https://www.ncbi.nlm.nih.gov/books/NBK430844/

StatPearls chapters are revised regularly. The "Updated" date tells your reader which version you read, so take it from the chapter page itself. The guides aren't consistent about whether to keep "[Internet]": South College keeps it, and JCU's chapter example drops it (In: StatPearls. NCBI Bookshelf version.). Pick one form and use it everywhere in the paper.

5. An UpToDate topic review

UpToDate topics have an author and a deputy editor, and the reference uses both:

Nieman LK. Measurement of cortisol in serum and saliva. In: Martin KA, ed. UpToDate. UpToDate; 2018. Accessed July 12, 2018. https://www.uptodate.com/contents/measurement-of-cortisol-in-serum-and-saliva

South College notes that UpToDate does not supply a URL in its own citation, "but the AMA manual recommends including one." Copy the topic's address from your browser's address bar. If you reached UpToDate through a library proxy, cut the proxy prefix so the link works for someone outside your institution.

6. A drug database entry: DynaMed, Martindale, MIMS

JCU combines the AMA database format with the chapter format. Its pattern is "Author AA, Author BB. Title of entry [type of entry, if applicable]. In: Editor AA, Editor BB, eds. Title of Database. Publisher. Published or updated date. Accessed date. URL."

` Propylthiouracil. In: DynaMed. EBSCO Information Services. Updated July 22, 2020. Accessed September 30, 2020. URL

Paracetamol. In: Brayfield A, ed. Martindale: The Complete Drug Reference. Pharmaceutical Press. Updated October 31, 2014. Accessed February 20, 2015. URL `

For DynaMed drug entries, JCU says to look for the last-updated date near the bottom of the page, under References. The guide also notes that AMA recommends citing a database as a whole and that JCU prefers citing the specific entry when possible. Your instructor's preference decides this, but the entry-level reference is more useful to a reader.

7. Micromedex and Lexidrug

South College gives a shorter form for these two, with no entry author and no "In:":

` Amoxicillin. Micromedex (electronic version). Merative; 2024. Accessed March 15, 2024.

Amoxicillin. Lexidrug. Wolters Kluwer Health; 2024. Accessed March 15, 2024. http://online.lexi.com `

The guide says a Micromedex reference must include "(electronic version)" and the Merative information. Check the publisher named on the product page at the time you read it.

8. A reference ebook on a platform like STAT!Ref

Domino FJ, Golding J, Stephens MB, et al., eds. What is evidence-based medicine? In: The 5-Minute Clinical Consult. Lippincott Williams & Wilkins Health; 2019. Accessed February 1, 2019.

South College tells you to leave out page numbers after the year for STAT!Ref ebooks, because the platform doesn't show the print pages. That example also uses "et al." for a group of four or more editors, which is how the library writes it. USC's rule (list up to six names in full) is the stricter reading of the manual, so check which one your program follows.

9. An entry with a type label: drug monographs and product information

Some databases hold several kinds of entry under one drug name. JCU puts the entry type after the title, either in parentheses or as a short label:

` Paracetamol (Systemic). Drug monograph. In: AusDI Database. Phoenix Medical Publishing. Updated May 28, 2020. Accessed September 1, 2020. URL

Prozac (Product information). In: MIMS Online. MIMS Australia. Updated September 2020. Accessed September 16, 2020. URL `

The label tells your reader which of several Prozac pages you mean. It costs a few words, and without it the reader may end up on the consumer leaflet when you used the prescribing information.

10. A chapter in a multi-editor reference handbook

Large pharmacology and clinical handbooks work like encyclopedias with chapter-length entries. USC's guide gives this one:

Relling MV, Giacomini KM. Pharmacogenomics. In: Brunton LL, Chabner BA, Knollmann BC, eds. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 12th ed. McGraw-Hill; 2011: 145-168.

Here the chapter authors and the three editors are all named, and all of them stay, since none of the lists reaches seven. The edition (12th) matters a great deal for a book like this, because chapters are rewritten between editions and page ranges move. Note that USC puts a space after the colon before the pages, while JCU's examples close it up (2012:3659-3660). Either way, use the same spacing in every reference.

In-text citations for encyclopedia entries

AMA citations in the text are superscript numbers. The JCU guide's summary is short: citations "are in superscript1 and in order of citation (the first citation is 1 the next is 2)," and "If you use the same source again, you keep the same number." If you cite an entry first and use it again after source 6, it is still number 1.

Placement follows USC's rule: "Place the superscript numbers just outside of periods and commas but inside of colons and semicolons."

The StatPearls chapter covers diagnosis of Achilles tendon rupture.¹ Two entries define the term the same way,¹,³ and a third does not.⁴ The UpToDate topic compares serum and saliva testing²; the dictionary gives the older usage.³

If your paper is in Vancouver style rather than AMA, the numbering logic is close but the punctuation differs. Our Vancouver citation guide covers that version.

Where to find each element

The pattern is easy to state. Most of the time goes into finding each piece on a page that was never laid out for citing.

• Entry author. Check the end of the entry as well as the top. JCU notes that contributors are sometimes identified only by initials at the end of an entry, so a signature there counts as an author.
• Editors. For print, look at the title page. For UpToDate, South College's pattern uses the topic's deputy editor. For StatPearls, the guides cited here leave the editors out and go straight to the title.
• Edition. UNC's Health Sciences Library says to include an edition number "if one is included as part of a title or is on the copyright page found on the back of the title page of the book." No edition shown means first edition, which AMA leaves out.
• Volume. On the spine and the title page of the volume you used. Give only the volume that holds your entry.
• Year. JCU's chapter elements call for the latest copyright year, which is on the copyright page.
• Updated date. For online entries, look near the top or bottom of the page for "Updated," "Last updated," or "Last modified." Use that date in place of a copyright year where the guides show one.
• URL. The address of the entry itself, copied from the address bar. A search results page or a proxy login page won't work for your reader.

Special cases

The entry has no named author

Start with the entry title, as in the Black's, USP and DynaMed examples above. JCU warns that "Contributors to encyclopaedias and dictionaries are sometimes identified by initials at the end of entries" and tells you to "Always look for an author before assuming there is not one." Look at the end of the entry, where print encyclopedias list contributors.

Neither an author nor an editor

Open with the entry title and go straight from "In:" to the title of the work. The Ceylon cinnamon bark oil example above has this shape.

Citing the whole reference work

If you mean the encyclopedia as a whole (say, you recommend a resource in a methods section), drop the entry title. JCU's example for a whole database is:

MIMS Online. MIMS Australia. September 2020. Accessed September 1, 2020. URL

Two entries from the same encyclopedia

Each entry is a separate source, so it gets its own reference and its own number, even when the editors, title and year match. The entries differ only in the entry title, and if they come from a print edition, in the page range.

The online entry has no date

Use what the page gives you. If it shows an "Updated" date, use that. JCU's Australian Medicines Handbook example shows the undated case: Liquid paraffin. In: Australian Medicines Handbook. Australian Medicines Handbook. Accessed September 1, 2020. URL. No published or updated date appears, and the accessed date carries the timing. The accessed date matters most for living references like UpToDate and DynaMed, because the text can change after you read it.

The entry has a DOI

Some publisher reference works assign DOIs to chapters. JCU's chapter examples end with the DOI in lowercase doi: form (doi:10.1007/978-1-4419-1681-5_12) and no period. USC's guide says book references take URLs and accessed dates rather than DOIs. The guides disagree here, so if your instructor or journal hasn't said which to use, choose one approach and use it for every book-type reference in the paper.

Wikipedia

None of the AMA 11 library guides checked for this post gives a Wikipedia example. If you have to cite it, the defensible choice is the AMA website pattern, which Purdue OWL's AMA electronic sources page lists as author or group, item title, website name, published date, updated date, accessed date and URL. Give the article title, Wikipedia, the date of the revision you read, the accessed date and the permanent link to that revision. For a clinical claim, the safer reference is the source the Wikipedia article itself cites, which you can read and cite directly. Our Wikipedia APA 7 guide shows how to find the permanent link, and the steps are the same whatever style you use.

You found the entry through a library database

Cite the reference work itself. The platform you used to reach it does not appear in the reference. Keep the publisher's own URL where one exists and remove any proxy prefix.

Common mistakes and how to avoid them

• Italicizing the entry title. The entry title stays in roman type and sentence case. Only the title of the work is italic. People make this mistake because the encyclopedia name and the entry name sit side by side.
• Putting the editors first when there is no author. Some generators and older guides move the editors to the start of the reference when the entry has no author. In the JCU pattern the editors stay after "In:", and the entry title moves to the front.
• Keeping the publisher's city. Philadelphia, PA: Elsevier; 2019 is 10th-edition form. In AMA 11 write Elsevier; 2019.
• Adding a period after the URL. In AMA 11 a reference that ends with a URL or DOI has no final period.
• Dropping the accessed date on an online entry. Online reference works change, and the accessed date is the only thing that fixes which version you read.
• Citing the database name as if it were the author. "UpToDate" is the title of the work and the publisher. The topic author goes first, and the deputy editor follows "In:".
• Numbering the same entry twice. Reuse the first number every time you cite the same entry again.
• Title-casing the entry. "Achilles tendon rupture" is right; "Achilles Tendon Rupture" is not. Proper nouns keep their capitals.

Quick-reference table