Q. Hello! I am providing guidance to art history students on creating bibliography and note entries and have a few questions that I’m not sure of the answer to: (1) How would one style the name Hans Holbein the Younger in a bibliography entry? (2) When a work of art doesn’t have a title and is simply a description, I assume it would be in sentence case and not italicized, but is this correct? For instance, this glass ribbed bowl at the Met. (3) I assume for guesstimate dates “ca.” would be preferred, but would “18th century” or “Edo period” be acceptable?
A. (1) For an item in a bibliography attributed to Hans Holbein the Younger, invert the name as “Holbein, Hans, the Younger.” (2) Yes, sentence case would be appropriate for a description in lieu of a title:
Glass ribbed bowl. 1st century BCE. Cast, tooled, and cut. Height 2 9⁄16 in. (6.5 cm), diameter 5 7⁄16 in. (13.8 cm). Metropolitan Museum of Art, New York. Object no. 17.194.197.
(3) Yes, a specific century or named era, if known, can be used instead of “ca.” (about), which usually applies to a more specific date such as a year. In some cases, it will be appropriate to combine a named period with an estimated date (e.g., Edo period, ca. 1800).
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. I’m wondering how you would treat an online report from an NGO or watchdog organization? What type of source is it parallel to? I’m asking to instruct my students for the author-date format. There is no specific author, just the organization. There is a specific date of publication, not just a year. This is the specific source, but there are others that are similar: https://humena.org/political-satire-in-egypt-a-peaceful-protest-against-repression/. Thank you.
A. Reports are covered briefly under CMOS 14.117, but you’ll also want to refer to 13.86 and 13.127, which show how to handle organizations as authors, including the use of abbreviations in author-date format.
Most freestanding reports can be cited similarly to books. The report at the URL you point to could be cited in a reference list as follows:
HuMENA and RedWord. 2024. Political Satire in Egypt: A Peaceful Protest Against Repression. HuMENA for Human Rights and Civic Engagement in collaboration with RedWord for Human Rights and Freedom of Expression, November 22. https://humena.org/political-satire-in-egypt-a-peaceful-protest-against-repression/.
As with many such documents, the author and publisher are the same. By abbreviating the author, you allow for concise citations in the text. The example above would be cited as “(HuMENA and RedWord 2024).”
Note that the report itself (published as a PDF file) doesn’t seem to list a date of publication, but the page that offers the PDF and announces its publication does have a date, which you can cite as shown above.
For working papers and the like, see CMOS 14.116.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Why do you use a colon to separate page numbers in a journal article citation but a comma to separate page numbers in most everything else? It seems completely nonsensical.
A. You’re right, a comma might make more sense. Somewhere along the line, however, the idea that a colon should come between a volume and page number morphed into Chicago’s current journal citation style. The following example, from the Botanical Gazette, appeared in the first ten editions of the Manual (the 1 in parentheses was used to mark the first of two examples by the same author):
LIVINGSTON, B. E., (1) On the nature of the stimulus which causes the change in form of polymorphic green algae. BOT. GAZ. 30:289–317. 1900.
That was offered not as an example of Chicago style but of Gazette style. Today, that same article can be found on the website of the International Journal of Plant Sciences (which continues the Gazette, a journal that got its start in 1876) and would be cited in modern Chicago style as follows:
Livingston, Burton Edward. “On the Nature of the Stimulus Which Causes the Change of Form in Polymorphic Green Algæ.” Botanical Gazette 30, no. 5 (1900): 289–317. https://doi.org/10.1086/328048.
An issue number and date now intervene between volume number and page range, but that colon nonetheless became Chicago style for citing journal articles, starting with the 12th edition (published in 1969). That was also the first edition to prefer Arabic rather than Roman numerals for volume numbers (the Gazette example was an exception to this rule in earlier editions), which may have factored into the decision. A colon remains Chicago style for referring to a volume and page number alone, as in “2:37” (for vol. 2, p. 37); see CMOS 14.74. Older Chicago style would have called for “II, 37” (with a Roman numeral and a comma, as in the 10th ed., ¶ 253).
The editors of the 12th edition could have specified a comma whenever a year or other number intervenes between volume and page numbers (as is the case for most journal article citations), but they didn’t. More than fifty years later, our editors have come to think of that colon as a helpful little sign that says journal article.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. A paper includes the following references:
Tawiah, Vincent, Ernest Gyapong, and Muhammad Usman. 2024. “Returnee Directors and Green Innovation.” Journal of Business Research 174 (March): 114369.
Tawiah, Vincent, Ernest Gyapong, and Yan Wang. 2024. “Does Board Ethnic Diversity Affect IFRS Disclosures?” Journal of Accounting Literature, ahead of print, September 24.
Tawiah, Vincent, Reon Matemane, Babajide Oyewo, and Tesfaye T. Lemma. 2024. “Saving the Environment with Indigenous Directors: Evidence from Africa.” Business Strategy and the Environment 33 (3): 2445–61.
Tawiah, Vincent, Abdulrasheed Zakari, and Rafael Alvarado. 2024. “Effect of Corruption on Green Growth.” Environment, Development and Sustainability 26 (4): 10429–59.
Should I still cite the first two references in the text as first author, second author, et al. YEAR (e.g., Tawiah, Gyapong, et al. 2024), even though only one author is not mentioned and so “et al.” doesn’t seem appropriate?
A. It would be nice if et al. (a Latin abbreviation meaning “and others”) could be used to refer to just one person, but it’s plural, and there’s no suitable alternative abbreviation for the singular.
In your situation—where you are obligated to include more than one name in your parenthetical author-date text references to distinguish between different works published in the same year by the same first-listed author but with different coauthors (otherwise, “Tawiah et al.” would suffice)—you have no choice but to include all three authors when citing any of the three sources by exactly three authors.
But you can still use et al. for the source by four authors (the article in Business Strategy and the Environment), where it would stand in for the names of the third and fourth authors (Oyewo and Lemma):
(Tawiah, Gyapong, and Usman 2024)
(Tawiah, Gyapong, and Wang 2024)
(Tawiah, Zakari, and Alvarado 2024)
but
(Tawiah, Matemane, et al. 2024)
Note that you’d need to list all three authors for the first two examples no matter what—because the first two authors are the same for both. It’s the third example (with coauthors Zakari and Alvarado) that requires all three names simply because et al. must refer to more than one person.
For some additional considerations (including the option to use a short title to differentiate such sources in text references, which would allow you to cite “Tawiah et al.” for all four of your sources), see CMOS 13.123. For the article ID in place of page numbers in the “Returnee Directors” citation, see CMOS 14.71. For the meaning of “ahead of print” in the Accounting Literature example, see CMOS 14.75.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. When citing an endnote, should the page number be the page the note callout appears on or the page where the endnote is at the end of the book (24n5 vs. 385n5)?
A. Footnote or endnote, you’re citing the note itself, not its reference number in the text. For an endnote, the page number to cite is the one at the end of the book where the note can be found (or 385n5 in your example).
This does mean that readers who follow the citation to its source will need to track down the note reference in the text if they want to see the context for that note, but endnotes are almost always less user-friendly than footnotes (unless the notes are linked, as in an ebook).
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. I’m in the middle of working with a client on a white paper that has citations to articles found on government agency websites (e.g., Centers for Disease Control and Prevention, National Institutes of Health, Office of Disease Prevention). The writing is completed, we’re in the layout/production stage, and while checking links and confirming URLs in the endnotes, we’re finding that articles and pages that had been referenced in our endnotes have now been removed from the government websites in accordance with the administration’s recent orders. How do we reference reports and articles that are significant but have been removed?
A. Whenever you find a dead link (or a link that works but points to a different version of the cited content), you have a few options, which are the same regardless of why the link no longer works as intended:
- If the cited page can’t be found anywhere, and the author didn’t save a copy, then you can either (a) add “(page no longer available)” or similar wording after the URL (as shown at CMOS 14.104), or (b) ask the author to revise the text and citation to fix the problem (perhaps by referring to and citing a different document). Option a should be used only as a last resort.
- If the author did save a copy, you can add that fact to the notice suggested for option a above: “(page no longer available; copy of original in author’s possession).” Option 1b may still be preferable unless the cited document is crucial to the author’s paper.
- If you can track down an archived version of the page—for example, at the Internet Archive’s Wayback Machine—you can cite that (after making sure that any text that relies on that page, including any direct quotations, remains accurate).
Option 3 is usually best, assuming the content has been archived in a way that allows others to consult it. For example, consider the following URL, which as of March 4, 2025, results in a “Page Not Found” notice:
https://www.cdc.gov/healthcommunication/Health_Equity.html
If you paste that URL into the Wayback Machine, you’ll find dozens of archived versions (or snapshots) dating back to August 25, 2021. Here’s how we’d cite one of those versions, following the recommendations at CMOS 14.104 (and using the “last reviewed” date reported at the bottom of that page in lieu of a publication date; see CMOS 13.16):
1. “Health Equity Guiding Principles for Inclusive Communication,” Gateway to Health Communication, CDC, last reviewed August 11, 2023, archived July 24, 2024, at https://web.archive.org/web/20240724170713/https://www.cdc.gov/healthcommunication/Health_Equity.html.
If you can’t find the page at the Wayback Machine or anywhere else, you’re back to options 1 and 2 at the beginning of this answer.
Links break for many reasons, but there are some basic precautions that authors can take to prevent the scenario described in the question above from happening in the first place:
- First, always save a copy of any web page (including any PDFs) that you consult as you do your research (e.g., as a screenshot or as an HTML or PDF file). Zotero and other citation managers can help with this task. See also CMOS 13.13 and 13.17.
- Second, don’t assume that a page will have been archived by someone else (as was the case for the CDC.gov URL in the example above). Instead, create your own archived version if you can—for example, by pasting the URL into the Save Page Now feature at the Wayback Machine. This won’t always be an option (some content will be blocked from being archived), but at least you’ll have your own personal copy to point to (see previous bullet) if anyone challenges your research.
Copyeditors can help by alerting authors to any page that may need to be archived or saved in one of the ways described above—and by editing citations accordingly. That should keep everyone, including readers, on the same page.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. I am wondering how best to cite, within one chapter of a multiauthor book, other chapters from the same volume. I am accustomed to simply adding “(see chapter X)” to the text, but one author is pushing back and wants to see them in the reference list. We are using author-date style.
A. Chapters in multiauthor books are likely to be consulted separately (and are sometimes offered for individual download or sale), so listing other chapters from that same book in the reference list at the end of your own chapter wouldn’t be the worst idea. But you should still let readers know that the chapter you’re citing is in the same book.
We’d suggest adding this information to the author-date reference for that chapter in your text—for example, like this: “(Smith 2025, in this volume).” The corresponding entry in your reference list would include the book’s title (per CMOS 13.109), so a similar comment shouldn’t be needed there:
Smith, Jane. 2025. “Chapter Title.” In Title of Book, edited by Joe Anyone. Publisher details.
If you cite more than a few chapters from your book, you may want to use a shortened form for the book: “In Anyone, Title of Book.” But even if you do that, you shouldn’t need to add a separate entry in the reference list for the book as a whole, the identity of which should be obvious to anyone who is already reading something from that book. For some additional considerations, see CMOS 14.10, under “author-date.”
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. CMOS 13.128 shows how to use author-date citations in a footnote, but what about an informational footnote like, “The history of exclusion of Chinese people in the United States has been highly researched. To begin, see . . .”? Should the parentheses around the citations be removed, as in “To begin, see Chan 1991, Lee 2003, and Kurashige 2016”? Otherwise, it might seem as though the citations are substantiating the statement, rather than being offered as suggested reading.
A. In Chicago style, the “see” in “see Chan” means that you’re referring to a work rather than a person, and the year would retain parentheses whether in the text or in a note: “To begin, see Chan (1991), Lee (2003), and Kurashige (2016).” If you’re instead referring to the author in terms of the work, the wording would need to make that clear: “See the earlier efforts by Chan (1991) to digitize the archival records.”
Parentheses for the year are omitted only when the citation is itself in parentheses, in which case semicolons rather than commas separate the sources, as in “(to begin, see Chan 1991; Lee 2003; Kurashige 2016).” But if your parenthetical reference is to an author rather than a work, the year would get square brackets: “(See the earlier efforts by Chan [1991] to digitize the archival records.)” See CMOS 13.122 and 13.124.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. I find ISBNs extremely useful when trying to locate copies of books of interest, especially when searching for secondhand copies of out-of-print books, for requesting books on interlibrary loan, and for disambiguating common names or titles. I’m writing a literature review in the form of an annotated bibliography and would like to include ISBNs in the entries for those books that have them, as a convenience and finding aid for readers. I can’t find any guidance for inclusion of ISBNs in Chicago-style footnotes or bibliography entries, even as an optional item. Can you provide a recommended template or example of placement and formatting?
A. Sure. Here’s how we’d recommend adding ISBNs to the bibliography entries for three different editions of Daniel James Brown’s bestselling book about a rowing team’s quest for Olympic gold at the 1936 Berlin Olympics (listed here in chronological order, from the 2013 Viking hardcover to the 2023 Penguin Books movie tie-in edition):
Brown, Daniel James. The Boys in the Boat. Viking, 2013. ISBN 978-0-670-02581-7.
Brown, Daniel James. The Boys in the Boat. Penguin Books, 2014. ISBN 978-0-143-12547-1.
Brown, Daniel James. The Boys in the Boat. Movie tie-in ed. Penguin Books, 2023. ISBN 978-0-593-51230-2.
In general, an ISBN or other optional information may be added to an entry in a bibliography when needed, following the period at the end of the other citation data. But if you need to include an ISBN within a note, we’d suggest adding it in parentheses, as part of the facts of publication:
1. Daniel James Brown, The Boys in the Boat, movie tie-in ed. (Penguin Books, 2023; ISBN 978-0-593-51230-2), 33–34.
The hyphens in the ISBN, which are optional, will help those who need to manually copy or type the number. For more on ISBNs and how they work, start with CMOS 1.36 and these FAQs from ISBN.org.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Hello, Chicago doesn’t seem to have an example of how to cite a contribution to a new edition of a book. Should the edition number follow a period or comma in the reference list entry below? Though my example is in Chicago 17 style, the question is still relevant for Chicago 18 style, so I would appreciate your guidance. Thanks!
Rothbard, Murray N. 2006. “The Libertarian Heritage: The American Revolution and Classical Liberalism.” In For a New Liberty: The Libertarian Manifesto, 1–23. 2nd ed. Auburn, AL: Ludwig von Mises Institute.
A. The best place for an edition number for a book is usually just after the title. When it’s part of an “In . . .” statement (as in your example), it follows a comma. As of the 18th edition, Chicago no longer requires a page range for a chapter or other contribution to a book or a place of publication, so your author-date entry would look like this:
Rothbard, Murray N. 2006. “The Libertarian Heritage: The American Revolution and Classical Liberalism.” In For a New Liberty: The Libertarian Manifesto, 2nd ed. Ludwig von Mises Institute.
(If you were following CMOS 17, the edition number would precede the page range: “. . . Manifesto, 2nd ed., 1–23. . . .”) In a reference list entry for the book as a whole, the edition number would follow a period:
Rothbard, Murray N. 2006. For a New Liberty: The Libertarian Manifesto. 2nd ed. Ludwig von Mises Institute.
Bibliography entries would follow the same pattern (except for the placement of the year of publication; see CMOS 14.1).
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]