Chicago Citation Guide (17th Edition): NB and Author-Date

Quick-Reference Table

The two Chicago systems share the same source data but arrange it differently. Use this table to see the core format at a glance.

Which System Should You Use?

Pick your system based on your field or your instructor's guidance. If you are writing history, literature, religion, philosophy, or art criticism, use the notes-bibliography system. If you are writing biology, sociology, economics, or most physical sciences, use the author-date system.

Some journals and departments specify one or the other in their style sheet. When in doubt, ask your editor or instructor before you start drafting. You can switch between systems later, but rebuilding hundreds of citations by hand wastes hours. A citation generator can save you that time by producing both formats from the same source data.

The Notes-Bibliography System

In NB style, each cited source appears twice: once as a footnote or endnote at the point of citation, and once in an alphabetized bibliography at the end of the paper. The footnote uses the author's name in natural order (First Last), while the bibliography entry inverts it (Last, First).

Footnote vs. Endnote

Footnotes appear at the bottom of the page where the reference is made. Endnotes appear in a list at the end of the chapter or paper. Chicago accepts either, but you should pick one and stick with it throughout the document. Most word processors let you toggle between the two without reformatting individual notes.

Superscript Number Placement

Place the superscript number at the end of the sentence or clause containing the reference, after any punctuation except a dash. If you are quoting directly, put the number after the closing quotation mark.

• Correct: The revolution began in 1789.¹
• Correct: "Liberty, equality, fraternity,"² became the rallying cry.
• Incorrect: The revolution began in 1789¹.

Full Note Format

The first time you cite a source, use the full note. It includes the author's name, the title, full publication details, and the specific page number you are referencing. Elements are separated by commas rather than periods.

Shortened Footnotes After the First Reference

After the first full citation, every subsequent citation of that same source uses a shortened note. The shortened form includes the author's last name, a shortened version of the title (usually the main noun phrase, not a subtitle), and the page number.

Example first note: 1. Eric Foner, The Fiery Trial: Abraham Lincoln and American Slavery (New York: W. W. Norton, 2010), 42.

Example shortened note: 2. Foner, Fiery Trial, 87.

The shortened title usually runs three or four words. Drop articles like the or a at the start if they make the short title awkward, but keep them when they belong to the phrase that identifies the work.

Ibid. Usage (and Why Chicago 17 Discourages It)

Older editions of Chicago relied on ibid. (Latin for "in the same place") to refer to the source cited in the immediately preceding note. The 17th edition now prefers shortened citations over ibid. because shortened citations remain clear when notes get reorganized during editing.

If you still choose to use ibid., it is lowercase, followed by a period, and followed by a comma and page number when the page differs from the previous note. Never use ibid. when the preceding note references more than one source.

Bibliography Format

The bibliography appears at the end of the paper on a new page under the heading Bibliography, centered. Entries are alphabetized by author surname, single-spaced within each entry, and double-spaced between entries. The first line of each entry starts at the left margin, and subsequent lines are indented half an inch (hanging indent).

Elements in a bibliography entry are separated by periods, not commas. The author's name is inverted (Last, First), and the specific page number is omitted because the bibliography describes the entire work.

Complete NB Examples by Source Type

Single-Author Book

Footnote: 1. Jill Lepore, These Truths: A History of the United States (New York: W. W. Norton, 2018), 214.

Shortened: 2. Lepore, These Truths, 301.

Bibliography: Lepore, Jill. These Truths: A History of the United States. New York: W. W. Norton, 2018.

Two or Three Authors

Footnote: 1. Michael Pollan and Judith Jones, Cooked: A Natural History of Transformation (New York: Penguin, 2013), 55.

Bibliography: Pollan, Michael, and Judith Jones. Cooked: A Natural History of Transformation. New York: Penguin, 2013.

Only the first author's name is inverted in the bibliography. For three authors, list all three separated by commas, with and before the final name.

Four or More Authors

In the footnote, list only the first author followed by et al.. In the bibliography, list up to ten authors in full; if there are more than ten, list the first seven followed by et al..

Footnote: 1. Robert Jones et al., Handbook of Cognitive Science (Cambridge: MIT Press, 2019), 102.

Bibliography: Jones, Robert, Sarah Kim, Li Wei, and Anna Patel. Handbook of Cognitive Science. Cambridge: MIT Press, 2019.

Journal Article

Footnote: 1. Anna Tsing, "Unruly Edges: Mushrooms as Companion Species," Environmental Humanities 1, no. 1 (2012): 141.

Shortened: 2. Tsing, "Unruly Edges," 143.

Bibliography: Tsing, Anna. "Unruly Edges: Mushrooms as Companion Species." Environmental Humanities 1, no. 1 (2012): 141-54.

For online articles, add a DOI at the end, formatted as https://doi.org/10.xxxx/xxxxx. If no DOI exists, include a stable URL.

Chapter in an Edited Book

Footnote: 1. Amartya Sen, "Equality of What?" in The Tanner Lectures on Human Values, ed. Sterling McMurrin (Salt Lake City: University of Utah Press, 1980), 204.

Bibliography: Sen, Amartya. "Equality of What?" In The Tanner Lectures on Human Values, edited by Sterling McMurrin, 197-220. Salt Lake City: University of Utah Press, 1980.

Website

Footnote: 1. Smithsonian National Museum of American History, "The First Ladies at the Smithsonian," accessed March 2, 2026, https://americanhistory.si.edu/first-ladies.

Bibliography: Smithsonian National Museum of American History. "The First Ladies at the Smithsonian." Accessed March 2, 2026. https://americanhistory.si.edu/first-ladies.

Include the access date for web content that lacks a publication or revision date. If the page shows a clear publication date, use that instead.

Newspaper Article

Footnote: 1. Michiko Kakutani, "Friendship Takes a Path That Diverges," New York Times, June 16, 2014.

Bibliography: Kakutani, Michiko. "Friendship Takes a Path That Diverges." New York Times, June 16, 2014.

Thesis or Dissertation

Footnote: 1. Sarah Chen, "Economic Networks in Late Imperial China" (PhD diss., Yale University, 2021), 88.

Bibliography: Chen, Sarah. "Economic Networks in Late Imperial China." PhD diss., Yale University, 2021.

The Author-Date System

The author-date system places a brief parenthetical reference in the text and matches it to a full entry in a reference list. This format is compact and keeps the reader's eye on the prose, which is why many sciences and social sciences prefer it.

In-Text Citation Format

The in-text citation includes the author's last name, the year of publication, and the page number when you are quoting or referring to a specific passage. Use a comma between year and page, and no punctuation between author and year.

• General reference: (Foner 2010)
• Specific page: (Foner 2010, 42)
• Author named in sentence: Foner (2010, 42) argues that...
• Two authors: (Pollan and Jones 2013, 55)
• Three or more: (Jones et al. 2019, 102)

Reference List Format

The reference list appears at the end of the paper under the heading References. Entries are alphabetized by author surname. The year of publication comes immediately after the author's name, which distinguishes this list from a bibliography.

Like the bibliography, entries use a hanging indent and separate elements with periods.

Complete Author-Date Examples by Source Type

Single-Author Book

In-text: (Lepore 2018, 214)

Reference: Lepore, Jill. 2018. These Truths: A History of the United States. New York: W. W. Norton.

Two Authors

In-text: (Pollan and Jones 2013, 55)

Reference: Pollan, Michael, and Judith Jones. 2013. Cooked: A Natural History of Transformation. New York: Penguin.

Journal Article

In-text: (Tsing 2012, 141)

Reference: Tsing, Anna. 2012. "Unruly Edges: Mushrooms as Companion Species." Environmental Humanities 1, no. 1: 141-54.

Chapter in an Edited Book

In-text: (Sen 1980, 204)

Reference: Sen, Amartya. 1980. "Equality of What?" In The Tanner Lectures on Human Values, edited by Sterling McMurrin, 197-220. Salt Lake City: University of Utah Press.

Website

In-text: (Smithsonian National Museum of American History 2026)

Reference: Smithsonian National Museum of American History. 2026. "The First Ladies at the Smithsonian." Accessed March 2, 2026. https://americanhistory.si.edu/first-ladies.

Multi-Author Work (Four or More)

In-text: (Jones et al. 2019, 102)

Reference: Jones, Robert, Sarah Kim, Li Wei, and Anna Patel. 2019. Handbook of Cognitive Science. Cambridge: MIT Press.

Multiple Works by the Same Author in One Year

When you cite two or more works by the same author published in the same year, distinguish them with lowercase letters after the year, assigned alphabetically by title.

In-text: (Smith 2020a, 15) and (Smith 2020b, 42)

Reference: Smith, Jane. 2020a. Early Essays. Boston: Beacon.

Reference: Smith, Jane. 2020b. Later Reflections. Boston: Beacon.

Common Mistakes

Professional and Academic Usage

University presses, scholarly journals in the humanities, and trade publishers in history and criticism expect Chicago NB. Most major journals in sociology, linguistics, and some natural sciences expect author-date. Graduate programs sometimes mandate one system across all coursework, so check your departmental handbook before submitting a dissertation proposal or thesis.

If you are preparing a manuscript for submission, follow the journal's specific house style sheet rather than the generic Chicago rules. Journals often modify Chicago in small ways, such as using numbered references instead of author-date, or requiring DOI links in a specific position. When you need to convert between styles quickly, the Rephrasely Citation Maker handles format switching for most major source types.

Turabian: Chicago for Student Papers

Kate Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations is the student-focused version of Chicago. The citation rules are effectively identical to Chicago 17, so anything you learn here applies directly to Turabian. The differences show up in page formatting rather than citation formatting: Turabian offers guidance on title pages, margins, and section headings specifically for class papers and theses.

If your instructor asks for Turabian, follow every Chicago citation rule in this guide, then consult the Turabian manual for paper layout. The two systems share the same bibliography, footnote, and reference list formats.

Frequently Asked Questions

When do I use notes-bibliography versus author-date?

Use notes-bibliography for humanities writing such as history, literature, and art criticism. Use author-date for sciences and social sciences. When a style guide or instructor specifies one, follow that instruction even if it conflicts with the field default.

Do I need both footnotes and a bibliography?

In most academic papers, yes. The footnotes give specific page references at the point of use, and the bibliography provides a complete, alphabetical list of every source consulted. Some shorter papers may allow footnotes only, but a full bibliography is standard for theses, books, and scholarly articles.

How do I shorten a title that has no clear main noun?

Pick the first few substantive words of the title that make it recognizable. Avoid dropping words that change the meaning. If the full title is A Problem from Hell: America and the Age of Genocide, a good shortened title is Problem from Hell.

What if the source has no author or no date?

If there is no author, begin the entry with the title. If there is no date, use n.d. in place of the year. For in-text author-date citations, use (Title n.d.) or (Organization n.d.) depending on what identifies the source.

Can I mix notes-bibliography and author-date in one paper?

No. Pick one system and apply it consistently. Mixing them confuses readers and signals that the manuscript was not proofread against a single style sheet.

Related Tools

• Citation Maker - generate Chicago footnotes, bibliography entries, and author-date references automatically.
• Plagiarism Checker - confirm your quotations and paraphrases are properly cited.
• Paraphraser - rewrite source material in your own words so you can cite and integrate it clearly.