---
name: citation-style
description: "Guides Chicago author-date citation and reference formatting per the Chicago Manual of Style (17th edition). Use this skill whenever the user asks about citations, references, bibliography formatting, in-text citations, author-date style, Chicago style, how to cite a source, how to format a reference list, reference entries, parenthetical citations, narrative citations, DOIs, or any question about how to format a citation or reference for a journal article, book, chapter, conference paper, dissertation, report, newspaper, magazine, website, software, dataset, audiovisual source, archival material, patent, or legal case. Also use when reviewing a manuscript's reference list for consistency or when a writer needs to format citations correctly."
---

# Citation Style: Chicago Author-Date

This skill covers citation and reference formatting in accordance with the Chicago Manual of Style, Seventeenth Edition (2017), using the author-date system. This is the standard for many academic journals and publishers.

## In-Text Citations

Citations appear in two forms:

### Narrative Citations
The author surname(s) appear as part of the sentence. The year follows in parentheses.
- `According to Singh and Harris (2018), this phenomenon occurs frequently.`
- `In 2018, Singh and Harris reported on the frequency...`

### Parenthetical Citations
The author surname(s) and year appear together in parentheses, placed at the end of a sentence before terminal punctuation.
- `This phenomenon occurs frequently in nature (Singh and Harris 2018).`

### Author Rules in Citations

| Authors | Citation Form |
|---------|-------------|
| 1 | Surname (Year) |
| 2 | Surname and Surname (Year) |
| 3 | Surname, Surname, and Surname (Year) |
| 4+ | Surname et al. (Year) |
| Organizational | Full name or abbreviation if reference uses one |
| No author | Short title in title case (Year) |

### Page Numbers with Quoted Passages
A comma separates year from page number: `(Liu et al. 2009, 124)` or for a range: `(Liu et al. 2009, 124–125)`.

### Multiple Citations
Arrange alphabetically by author surname; separate with semicolons: `(Abbas and Ludden 2018; Carlyle 1997; Carlyle et al. 1997)`

### Same Author, Same Year
Add lowercase letter designators: `(Murakami 2003a, 2003b)`

### Secondary Sources
Use "quoted in": `(Huang and Zoller 1995, quoted in Zhu 2010, 18)`

## Reference List

The reference section appears at the end of the text under the heading "References." It includes entries for all works cited. Entries use hanging indent format.

### Ordering Rules
1. Alphabetical by first author's surname
2. Same first author → alphabetical by subsequent authors
3. Same full author list → chronological by publication date
4. Same authors and year → alphabetical by title, with letter designators (a, b, c)
5. Organizational authors ordered alphabetically by name/acronym
6. No credited author → alphabetical by title among other entries

### Author Formatting in References
- First author: Surname, Given Name(s) or Initial(s).
- Subsequent authors: Given Name(s) Surname (not inverted)
- 2–10 authors: list all, "and" before final name
- 11+ authors: list first seven, then "et al."
- Do not replace repeated names with dashes

### Titles
- Journal/magazine/newspaper titles: italicised, title case, no quotation marks
- Article/chapter titles: roman font, quotation marks, title case
- Book/report titles: italicised, title case

### URLs and DOIs
- DOIs close journal article entries (when available)
- URLs close web and other electronic resource entries
- Access dates recorded only when no publication date can be determined

## Quick Formatting Checklist

- [ ] All in-text citations have corresponding reference entries (and vice versa)
- [ ] Author names formatted correctly (inverted first author, non-inverted subsequent)
- [ ] 4+ authors use "et al." in citations, full list (up to 10) in references
- [ ] Publication years present on all entries (or "n.d." / "forthcoming")
- [ ] Journal articles include volume, issue number, page range, and DOI
- [ ] Book entries include city and publisher
- [ ] Titles use correct capitalisation and formatting (italic vs. quotation marks)
- [ ] Reference list alphabetised correctly
- [ ] Same-author/same-year entries have letter designators
- [ ] Hanging indent format throughout reference list

## When to Read Reference Files

- **For detailed in-text citation rules** (placement, authors, years, special cases) — read `references/citation-rules.md`
- **For general reference list formatting rules** (ordering, author lists, titles, URLs/DOIs) — read `references/reference-list-rules.md`
- **For journal article reference models** with examples — read `references/journal-article-models.md`
- **For book and book chapter reference models** with examples — read `references/book-and-chapter-models.md`
- **For all other source types** (conferences, dissertations, reports, newspapers, magazines, web, software, audiovisual, unpublished, archival, legal) — read `references/other-source-models.md`
