Chicago/Turabian Referencing: Notes-Bibliography and Author-Date

Chicago style is the standard citation system in academic history, and is widely used in philosophy, literature, theology, and arts disciplines. It also has a social science variant. Unlike APA and MLA, Chicago offers two distinct citation systems — and using the wrong one for your discipline is a common error.

Two systems: which one do you need?

Notes-Bibliography (NB) — Used in history, literature, philosophy, theology, arts, and fine arts. Citations appear as numbered footnotes or endnotes; sources are also listed in a bibliography at the end.

Author-Date (AD) — Used in social sciences, natural sciences, and economics. In-text parenthetical citations (Smith 2021, 45); sources listed in a reference list at the end.

When in doubt, history always uses Notes-Bibliography. If your department says "Chicago style" without specifying which system, it is almost certainly Notes-Bibliography.

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Notes-Bibliography System

How footnotes work

In the body of the essay, place a superscript number immediately after the cited passage, before any punctuation except a dash:

The testing effect has been described as "one of the most robust phenomena in cognitive psychology."¹

The evidence for spaced repetition is similarly strong,² though the optimal spacing interval remains debated.³

At the bottom of the page (footnote) or end of the document (endnote), each number gets a full citation on first use, and a shortened citation on subsequent references to the same source.

First footnote: full citation

Book:

1. Alan Baddeley, Michael Eysenck, and Michael Anderson, Memory, 
   3rd ed. (London: Psychology Press, 2020), 45.

Journal article:

2. Henry Roediger and Jeffrey Karpicke, "The Power of Testing Memory: 
   Basic Research and Implications for Educational Practice," 
   Perspectives on Psychological Science 1, no. 3 (2006): 181–210.

Chapter in edited book:

3. Sarah Brown, "Working Memory in Academic Contexts," in Learning and 
   Cognition, ed. Jane Smith and Alan Jones (London: Routledge, 2021), 
   102–125.

Website:

4. Jane Smith, "How Spaced Repetition Works," BBC Future, March 15, 
   2023, https://www.bbc.com/future/article/20230315.

Subsequent footnotes: shortened citations

After a source has been given in full, subsequent references use a short form:

5. Baddeley, Eysenck, and Anderson, Memory, 87.
6. Roediger and Karpicke, "The Power of Testing Memory," 195.

Ibid. can be used when citing the same source as the immediately preceding note:

7. Baddeley, Eysenck, and Anderson, Memory, 120.
8. Ibid., 122.

Bibliography

The bibliography appears at the end of the essay on a new page. Unlike footnotes, bibliography entries:

• List the author's last name first
• Are sorted alphabetically by author's last name
• Use hanging indentation
• Do not include page numbers for the full work (books) but do for articles

Book:

Baddeley, Alan, Michael Eysenck, and Michael Anderson. Memory. 
   3rd ed. London: Psychology Press, 2020.

Journal article:

Roediger, Henry L., and Jeffrey D. Karpicke. "The Power of Testing 
   Memory: Basic Research and Implications for Educational Practice." 
   Perspectives on Psychological Science 1, no. 3 (2006): 181–210.

Note the difference between footnotes and bibliography:

• Footnotes: first name first, commas between elements
• Bibliography: last name first, elements separated by periods

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Author-Date System

In-text citations

The Author-Date system uses parenthetical citations with the author's last name, year, and page number:

Situation	Format	Example
Standard	(Author Year, page)	(Smith 2021, 45)
Author in sentence	Author (Year, page)	Smith (2021, 45) argues...
Two authors	(Author and Author Year, page)	(Smith and Jones 2021, 45)
Three or more	(Author et al. Year, page)	(Smith et al. 2021, 45)
No page (e.g., website)	(Author Year)	(Smith 2021)

Note: Chicago Author-Date does not use a comma after the author's name (unlike APA). The format is (Smith 2021, 45) not (Smith, 2021, p. 45).

Reference list

The reference list is alphabetical and uses the same information as the bibliography but formatted slightly differently:

Book:

Baddeley, Alan, Michael Eysenck, and Michael Anderson. 2020. Memory. 
   3rd ed. London: Psychology Press.

Journal article:

Roediger, Henry L., and Jeffrey D. Karpicke. 2006. "The Power of 
   Testing Memory: Basic Research and Implications for Educational 
   Practice." Perspectives on Psychological Science 1 (3): 181–210.

The key structural difference from Notes-Bibliography: the year moves to after the author's name in the reference list.

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Common Chicago mistakes

Confusing footnote and bibliography format — These are different. Footnotes put first name first and use commas; bibliographies put last name first and use periods. Mixing them up is one of the most common Chicago errors.

Using "p." or "pp." for page numbers — Chicago does not use p. or pp. for footnote page citations. Just write the number: (Smith 2021, 45) or ¹ Smith, Memory, 45.

Not shortening subsequent footnotes — After the first full citation, use the shortened form. Repeating the full citation for every reference is non-standard and clutters footnotes.

Using Author-Date when your subject expects Notes-Bibliography — If you are writing a history essay and using (Smith 2021, 45), your marker will notice. Check which system your department uses.

Missing bibliography entries — Every footnote must have a corresponding bibliography entry. Use the bibliography to double-check that nothing is missing.

For automatically formatted Chicago citations, use the Citation Reference Formatter. For other styles, see the MLA Guide, APA Guide, and Harvard Guide.