Chicago, from Citation Styles and Their Uses, offers two systems. Its notes and bibliography system, common in history and the arts, puts a small number in the text1 and the source in a numbered footnote (or endnote), with a bibliography at the end. Its author-date system works much like APA.
| Kind | Example (an invented practice book) |
|---|---|
| First note | 1. Ellen Marsh, The Quiet Garden: Growing Food in Small Spaces (Larkspur Press, 2019), 42. |
| Later note | 2. Marsh, Quiet Garden, 57. |
| Bibliography entry | Marsh, Ellen. The Quiet Garden: Growing Food in Small Spaces. Larkspur Press, 2019. |
Key idea
A note gives the source in reading order (First Last, Title (Publisher, year), page). Later notes are shortened: last name, short title, page. The bibliography inverts the first author’s name and uses periods. The 18th edition prefers shortened notes to ibid.
Why it works
Notes let a writer cite and comment on sources without interrupting the main text, which suits history, where sources are discussed in detail. Shortened notes are clearer than ibid. (“in the same place”): the reader sees the source’s name at once instead of hunting back through earlier notes.
Worked example: Note to bibliography
Turn the note “Maria Delgado, “Sleep and Memory in Middle School Students,” Journal of Student Health 14, no. 3 (2022): 205.” into a bibliography entry.
- Invert the name: Delgado, Maria.
- Periods between main parts instead of commas.
- Give the article’s full page range instead of one page: 201–19 (Chicago shortens the second number).
Answer: Delgado, Maria. “Sleep and Memory in Middle School Students.” Journal of Student Health 14, no. 3 (2022): 201–19.
Worked example: Ibid. or a short note?
Note 4 cites Marsh, page 42. Note 5 cites Marsh again, page 60. What should note 5 say?
- Ibid. would work, since note 4 is the same source, but Chicago 18 discourages it.
- The preferred form is the shortened note.
Answer: 5. Marsh, Quiet Garden, 60.
Common mistake
Using Ibid. everywhere. The 18th edition prefers shortened notes and discourages ibid., which can only ever point to the source of the note just before. If a note for another source comes between, ibid. would point to the wrong one.
Other Chicago 18 changes: the place of publication is no longer needed for books published after 1900, and a bibliography entry lists up to six authors before “et al.” Chicago 18 also accepts singular they. The sources in these examples are invented for practice: the authors, titles and publishers are made up.