Citation Styles

Chicago author-date system combines in-text citations with a References list at the end of a paper. Typically, this system is used within the physical, natural, and social sciences disciplines. However, it can be adapted for any field. At times, footnotes or endnotes can be used to provide supplemental information. In this case, composing notes in author-date system follow similar rules to composing notes in notes-bibliography system.

In Chicago Manual of Style, regardless of system, "source citations must always provide sufficient information either to lead readers directly to the sources consulted or ... positively identify them, regardless of whether the sources are published or unpublished or in printed or electronic form." (CMOS,14.1)

You are required to cite sources within the text (or body) of the paper using the author-date citation system. This system consists of an in-text citation and a reference list entry. Every resource cited in the body of your paper must be listed alphabetically in the references list. Likewise, every resource in the reference list must be cited in the body of your paper.

• The exceptions are personal communications you've had with others, general mention of whole websites or periodicals, or general mention of common software and applications. While they have in-text citations or mentions in the text, they are not included in the reference list.
• Common knowledge is also not required to cite.

Chicago author-date style requires specific kinds of information be included in in-text citations. The author's last name and the work's date of publication must always appear & are all that is necessary when citing an idea, an entire book, article or other work. Example: (Roberts 2009). These must match exactly the corresponding entry in the references list. The page number appears only if it is a direct quotation or if it's useful for location. 

Placement of the citation may vary within the body of your paper. There are some options of where to place the citation in text.

• Narrative Citation:
  • The name of the author can be incorporated into the narrative of the paper. Example: In his study of how teenagers use social media, Roberts (2009) found ...
  • The name of the author and the date may also be stated in the narrative without parentheses. Examples: In 2009, Roberts examined how teenagers use social media to following ways ...
• Parenthetical Citation
  • Both the name and date of the work cited appear at the end of a sentence enclosed in parentheses. Example: Researchers studying how teenagers use social media found that ... (Roberts 2009)

No matter if using a narrative citation or a parenthetical citation, a page number appears if it is a direct quotation or if it's useful for location.

• Narrative Citation Example: In 2009, Roberts found that "teenagers use social media for..." (195)
• Parenthetical Citation Example: (Smith 2009, 195)

SUMMARIZING OR PARAPHRASING

Groups as Authors: When the author is a group (association, corporation, government entity etc.), their name is generally spelled out each time it appears in a text citation. If the group's name is long and/or there is a well known abbreviation, use it in subsequent in text citations.
Examples: First time: (Mothers Against Drunk Driving 2009); Subsequent uses: (MADD 2009).

No Author: Use the first few words of the reference (usually the title) and the date. Use double quotations marks around the title of an article, a chapter or web page and italicize the title of a journal, book or report.
Examples: ("Comparing learning styles" 2009) OR (Learning the Alphabet 2009).

No Date: If the date of publication is missing or unknown, use the abbreviation "n.d."

Indirect Sources: When you use a source cited in another source, name the original source in the narrative. The secondary source [the one you used] should be listed in your reference list and cited in parentheses. Example: Johnson's study of teenagers found ... (as cited in Roberts 2009).

Electronic Sources: Generally, electronic sources cited within the text should be treated the same as print sources. Include the author's name (or brief title if there is no author) and date in parentheses.

DIRECT QUOTATIONS:

Short Quotations: If you directly quote from a source and the quotation is 40 or fewer words include it in the text and enclose it with double quotation marks. Examples: (Roberts 2009, 195) OR Roberts (2009) found that "teens' uses of social media included ..." (78).

Long Quotations: When you quote directly from the source and the quotation is more than 40 words display it in a free standing block without quotations. Quotation block should appear on a new line indented at least 5 spaces from the left margin and be double-spaced.

Online Sources: Credit online sources using the authors' name, date and page numbers in the same manner as print sources. If there are no page numbers but chapters are visibly numbered use them in place of page numbers. Use the abbreviation "chap." in place of the page number. Examples: (Roberts 2009, chap. 3)

The 17th edition of Chicago author-date style has a references list of all cited sources. Although formatting is similar to APA's reference list, there are some differences.

Title: On a new page after your paper, enter the word "References" and center it. Depending on your professor's preference, the title can also be "Works Cited." Do not bold, italicize, underline or use quotation marks. "Bibliography" is not used as a title at all. 

Order: Entries are organized alphabetically by the author's last name. If working with multiple sources by the same author or with works with no listed author, organize those sources alphabetically by title. 

Indentation: The first line of each reference entry is flush left with the margin. Indent all subsequent lines by half an inch. 

Spacing: Unlike reference entries in APA style, reference entries in Chicago author-date system are single-spaced, with one line space in between entries.

Punctuation: All entries in the references list end with a period. Periods separate most entry elements. Colons follow the publication location, and commas follow the publisher before the publication year. Parentheses do not enclose publication facts.

Authors: The first-listed author’s name is inverted (last name, first name), but subsequent authors are listed as normal without a separating comma (first name last name). Include all authors' names in the reference list. Use "and" to separate authors as needed.

Multiple Works by Same Authors: If working with multiple works by the same author, organize them alphabetically by title.

No Author: If the author is unknown or not listed, the reference entry should begin with a title. Follow formatting depending on the source type. Do not alphabetize by articles (an, a, the). If the author is listed as "Anonymous," use "Anonymous" as the author's name. 

Publication Date: Unlike in notes-bibliography style, the publication date follows the author's name. 

Capitalization: In titles of smaller works and larger works, capitalize all important words.

Italics and Underlining: Italics is used for book titles, magazine or newspaper publications, and journal titles. Underlining is not used in citations, including for DOIs or URLs.

Quotation Marks:  Enclose the title of articles, book chapters, presentations etc. in quotation marks. Use a period inside the closing quotation mark.

Abbreviations: Editions, editors, and translators are abbreviated to "ed.," "eds.," and "trans.," respectively. Spell out "edited by" and "translated by" if they're used. Issue numbers are abbreviated with "no.," but do not abbreviate volume numbers with "vol."  

Pagination: No matter the source type, the abbreviations "p." or "pp." are not used to signify page numbers. Dashes are used for sequential pages, while commas are used for non-sequential pages.

Digital Object Identifier (DOI): A unique DOI is assigned to journal articles and always begins with a 10. DOIs provides persistent links to articles, eliminating issues with website URLs changing. However, not all articles have a DOI; additionally, DOIs are visible in some databases but "hidden" in others. If available, a DOI should be listed at the end of the citation.

URLs: URLs are used whenever a DOI is not used or found. If there isn't a DOI but the specific URL to the page makes it inaccessible, use the home page URL of the journal or book publisher. For articles, try to include the URL specifically leading to the article.