Social sciences/sciences or author-date style: Chicago/Turabian (17th ed.) citation guide



There are two varieties of Chicago style.

This page includes examples of citations in the author-date system found in The Chicago Manual of Style (17th ed.). This system is more common in the social sciences and sciences.  

The author-date system is related to the notes and bibliography system covered in the rest of the Chicago citation guide (and used mainly in the humanities) -- but there are some differences.


Basics of the author-date system

In the author-date system (used most often for social sciences or sciences), citations for sources must appear in two places in your essay (15.5):

  • in the in-text citations, the text of your paper when you refer to the source 
  • in the reference list, also known as the bibliography (at the end of your paper)

Each in-text citation must match with a reference list entry. You are responsible for the accuracy of all information in your in-text citations and reference list (13.6).

If you are not sure which Chicago style system you are being asked to use, check with your instructor.

In-text citations (15.7, 15.21-15.31)

A basic in-text citation requires the author’s last name followed by the year of publication inside parentheses. (15.7)

(Liu 2016)

When quoting a specific passage, also include the page number after a comma. (15.7)

"Direct quotation" (Cartwright 2003, 146)…
According to Cartwright, a “direct quotation” is often used (2003, 146)…

When using multiple works in the same citation, separate them with a semicolon. (15.7)

(Bradbury 1953; Willis 1997)

When citing works from the same author published in different years, use the author name once and separate the years with commas. (15.30)

(Jemisin 2015, 2016, 2017)

When citing works from the same author and year, distinguish them by putting letters after the year. (15.20)

(Blythe 2001a, 2001b)

For a work by two or three authors, include the last names of all authors in text. (15.9)

(Simon and Garfunkel 1970)    
(Crosby, Stills, and Nash 1969)

For a work by four or more authors, cite only the last name of the first named author in text, followed by et al. (15.9, 15.29)

(Weatherby et al. 2017)
Based on a case study by Weatherby et al. (2017)…

If there is no author given, you may use the organization or publisher responsible for the work, abbreviated as needed in text but additionally spelled out in the reference list. (15.37) 

(Wizards of the Coast 2014)
(CBC 2019a, 2019b)

If you cannot find the author or organization responsible, use the title of the work instead, shortened to four words or fewer in text and listed in full in the reference list at the end. (15.39)

(“Meanest Thieves Steal Blankets” 1908)

If there is no date of publication, use n.d. in place of the year. (15.44)

(Crowley n.d.)

Reference lists or bibliographies (15.6, 15.10-15.20)

Rules for reference lists  using the author-date system are largely the same as the notes and bibliography style described elsewhere in this guide.

The main difference is that the year of publication appears directly after the author’s name, as seen in these examples. (15.3, 15.6)

Sample citations in reference lists

Author-date system

Callaway, Ewen. 2014. "Chicken Project Gets off the Ground." Nature 509, no. 7502: 546.

Piller, Ingrid. 2016. Linguistic Diversity and Social Justice: An Introduction to Applied Sociolinguistics. New York: Oxford University Press.

Notes and bibliography system

Callaway, Ewen. "Chicken Project Gets off the Ground." Nature 509, no. 7502 (2014): 546.

Piller, Ingrid. Linguistic Diversity and Social Justice: An Introduction to Applied Sociolinguistics. New York: Oxford University Press, 2016.

Building a reference list

To build a reference list using the author-date system, you can use other pages in this guide or section 14 of The Chicago Manual of Style, then move the publication year to be after the author’s name.

Get help

For special cases or questions, see Chapter 15 of The Chicago Manual of Style either in print or online, or Ask a Librarian.