Citation Guide

Chicago Author-Date: Essential Rules

How often to cite?

  • Remember: one citation at the end of a string of sentences or a paragraph cannot “cover” the entire section.
  • Cite a source the first time it is used in each paragraph.
  • Every sentence thereafter in the paragraph that uses information from this same source must contain either a signal phrase or a citation clearly indicating where the information came from.
    • Note: always use a citation (even if you also use a signal phrase) every time you quote material.

In-text Citation Placement

Where in the sentence does my in-text citation go?


  • If you name your source(s) in a given sentence, a parenthetical citation containing only the year always follows immediately after the name(s) of the author(s). Example: In contrast to earlier work by Abbott and Costello (1999), Laurel and Hardy (2008) propose an altogether different model for optimizing hat density.
  • If you do not explicitly name your source(s) in a given sentence, a single parenthetical citation goes at the end of the sentence or clause it covers (Goffman 1974), inside the punctuation, like this (Melville 1851).
    • “If the sentence ends with a quotation, close the quote, then place the citation between the quotation marks and the punctuation, like this” (Woolf 1931, 14).
  • Do not insert spaces between a parenthetical citation and the punctuation that follows it.

In the paragraph below, the  parenthetical in-text citations are highlighted in yellow, and the signal phrases are in blue. Note that the second sentence is common knowledge, whereas the final sentence is clearly the opinion of the author.

In a 2009 Journal of Restaurant Marketing article, restaurateur Shawna Jackson contends that a restaurant’s color scheme influences how hungry its patrons are. Consider popular fast-food restaurants, which often use red and yellow in their advertising and décor. According to a study by Roberta Chen and David Lopez (2016), restaurant customers feel energized in red and yellow environments, which encourages them to order more food. The same study indicates that patrons feel relaxed in blue and purple environments, which encourages them to “spend more time considering the menu options and eat at a slower pace” (29). Although blue décor can give your restaurant a more casual, laid-back feel (Chen and Lopez 2016), Jackson believes it encourages patrons to linger at their tables without ordering additional food or beverages. Accordingly, it is difficult to identify a popular chain restaurant that decorates with calmer hues.

For more information, see the TPO's Citing Responsibly in Chicago Author-Date (PDF).

Bibliography / List of References

What is the difference between them?

  • A Bibliography lists all works cited and consulted
  • A List of References includes all works cited in a text

The NPS Thesis Processing Office prefers a List of References for the following: 

  • Thesis
  • Capstone project report
  • MBA report
  • Dissertation

Author Names: Honorifics

Do not include honorifics (Dr., Col., Professor, etc.) when citing author names. Including these titles in the body of your document is acceptable.

Identifying Organizational Authors

Official Documents

The author is the organization immediately responsible for creating the document. In this example, the author is the Office of the Chief of Naval Operations and the publisher is the Department of the Navy.

organizational author


The author is NOT an umbrella organization, signatory, or any of the following:

  • Chief of Naval Operations
  • Deputy Chief of Naval Operations
  • W. F. Moran
  • Department of Defense
  • Navy Pentagon
  • R. P. Burke

Do not include acronyms for organizations listed as authors in the List of References or footnotes:

  • YES: Office of the Chief of Naval Operations.
  • NO: Office of the Chief of Naval Operations (CNO or OCNO).
  • NO: CNO or OCNO.

Same Author, Multiple Works / Multiple Sources in One Citation

Examples given for books; follow appropriate style for the source type you are citing.

Examples given are for books; follow the appropriate style for the source type you are citing.

Source Generic Example Actual Example

Same author, same year, different sources

  • List sources in alphabetical order by title in the List of References (ignoring initial "a," "an," or "the") and append a lowercase letter to the year.
Source 1

R: Author Last Name, Author First Name. Year published + a. Title of Book 1 in Title Case and Italics. Place of Publication: Publisher.

T: (Author Last Name year + a)

R: Hawthorne, Pat. 2006a.The Cannibal’s Dilemma: An Unnatural History of Four Siblings. New York: Penguin.

T: (Hawthorne 2006a)

Source 2

R: Author Last Name, Author First Name. Year published + b. Title of Book 2 in Title Case and Italics. Place of Publication: Publisher.

T: (Author Last Name year + b)

R: Hawthorne, Pat. 2006b. Having People for Dinner: A Guide for the Home Cook. New York: Penguin.

T: (Hawthorne 2006b)

Combined T (both sources): (Author Last Name year + a, year + b) T (both sources): (Hawthorne 2006a, 2006b)

Same author, different year, different sources

  • List sources in chronological order.
Source 1

R: Author Last Name, Author First Name. Year published. Title of Book 1 in Title Case and Italics. Place of Publication: Publisher.

T: (Author Last Name year, page)

R: Hawthorne, Pat. 2006. Having People for Dinner: A Guide for the Home Cook. New York: Penguin.

T: (Hawthorne 2006, 99–100)

Source 2

R: Author Last Name, Author First Name. Year published. Title of Book 2 in Title Case and Italics. Place of Publication: Publisher.

T: (Author Last Name year)

R: Hawthorne, Pat. 2008. Regrets. New York: Penguin.

T: (Hawthorne 2008)
Combined T (both sources): (Author Last Name year 1, year 2) T (both sources): (Hawthorne 2006, 2008)

Different authors, different years

  • Place references in alphabetical order and separate them with a semicolon. Ensure all authors appear in the list of references.
  • "Where two or more works by different authors with the same last name are listed in a reference list, the text citation must include an initial (or two initials or a given name if necessary)" (CMS 15.22).

T: (Author 1 Last Name year; Author 2 Last Name year)

T: (Fiddleywink and Snort 2005; Munglesnee, Grumpernickel, and Smith 1995; Otatop 2007).

T: (Q. Fiddleywink 1975; Z. Fiddleywink 1982)


Capitalization (Title Case / Sentence case)

Title Case Sentence case
Love among the Ruins: A Memoir of Life and Love in Hamburg, 1945 Love among the ruins: A memoir of life and love in Hamburg, 1945

Capitalize everything except:

  • conjunctions (and, but, or, etc.)
  • prepositions (to, of, on, among, between, etc.)
  • articles (a, an, the)

Capitalize only:

  • the first and last words in titles and subtitles
  • proper nouns


Note: Always format the information in your citations (titles, author names, etc.) according to the requirements of the citation style you are using, regardless of how it appears in the original source.

Missing Info

If any information is missing from a source (a journal with no volume number, for example), simply omit that information. For sources consulted in hardcopy, omit the URL and any additional verbiage that introduces it. Anything retrieved online, however, MUST have a link. The only exception is journals retrieved from a subscription database such as ProQuest. 

Page Numbers

For direct quotes, add page numbers to the in-text citation only.

Example: (Haynes 2009, 70)

For book chapters, include page-number range in List of References/Bibliography.

Example: Cordesman, Anthony H., Adam Mausner, and David Kasten. 2009. Introduction. In Winning in Afghanistan: Creating Effective Afghan Security Forces, edited by John Smith, 1–12. Washington, DC: Center for Strategic and International Studies.

Print vs. Online

When citing a source retrieved online, use the "online" format even when you or someone else printed out the material. For example, if you print out a thesis or your advisor provides you with a printed thesis, it is still categorized as an online document.

Only cite as a print source when the material has been produced by a publisher in hard copy. For example, if you obtain a print journal or book from the library stacks, it is categorized as a printed source.

Accessed Date and URL Formatting

  • Only include date accessed if the source material has no date.
  • Always include a period at the end of the URL.
  • Do not insert a hard or soft return within the URL string; doing so breaks the link.
  • A URL does not belong in an in text-citation. Ever.

Et al.

  • Up to three authors:
    • In the reference list, include all of them
    • In the text, include all of them
  • Four to ten authors:
    • In the reference list, include all of them
    • In the text, list only the first author, followed by et al. (“and others”)
  • More than ten authors:
    • In the reference list, include only the first seven, followed by et al.
    • In the text, list only the first author, followed by et al.

Secondary Sources

A secondary source is a source that cites some other work that you discuss in your text.

Whenever possible, consult primary sources and your sources’ sources yourself. Upon investigation of the primary source, you may find you disagree with the secondary source author’s analysis or methods. Only use secondary sources when the primary source is unavailable.

How to Incorporate Secondary Sources

The following passage incorporates a properly credited secondary source. The secondary source information is highlighted in yellow; the primary source information is highlighted in blue.

Walker (2008) describes data collected in 1999 by Miguel Roig that correlates students’ inadequate paraphrasing to poor reading comprehension. Citing Roig’s data, Walker explains that “students do in fact possess skills necessary for paraphrasing but … may be impeded from applying those skills when dealing with rigorous text” (387).

Note: Include  only  the  secondary  source  (the  source  you  consulted)  in  your  reference  list. 


For more information

See the TPO's "Citing Your Sources’ Sources" handout.

No Date Given

To cite an undated document, use n.d. (no date).

Additional Resource