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How to Cite Two Works by the Same Author in the Same Year

When one author publishes twice in a year, an author–date citation stops identifying a single work. APA 7 and Chicago 18 author-date solve that with lowercase letters after the year, assigned in title order. MLA 9 never had the problem, because its parenthetical is author–page, so it distinguishes the works by shortened title and marks the repeated name in the works-cited list with three hyphens. Chicago notes-bibliography also relies on titles, and since CMOS 17 repeats the author's name in every bibliography entry instead of using a 3-em dash. This guide is the disambiguation workflow; the ordering rules for a whole reference list are in how to write a bibliography.

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Quick Answer: two works, one author, one year

Sort the two works alphabetically by title, ignoring an initial A, An, or The. In APA 7 and Chicago author-date, the first becomes 2020a and the second 2020b, in the list and in every in-text citation. In MLA 9, add a shortened title after the author's name in the parenthetical and replace the author's name with --- in the second works-cited entry. In Chicago notes-bibliography, shortened notes already carry the title, and the bibliography repeats the author's full name in each entry, alphabetised by title.

Templates for Halloran's two 2020 articles

APA 7 references:

Halloran, D. (2020a). Attention budgets … / Halloran, D. (2020b). Noise, focus …

APA 7 in-text:

(Halloran, 2020a); (Halloran, 2020b); both at once (Halloran, 2020a, 2020b)

MLA 9 works cited:

Halloran, Deirdre. "Attention Budgets …" / ---. "Noise, Focus …"

MLA 9 in-text:

(Halloran, "Attention Budgets" 104); (Halloran, "Noise" 360)

Chicago 18 shortened notes:

2. Halloran, "Attention Budgets," 104. / 3. Halloran, "Noise, Focus," 360.

Chicago 18 bibliography:

Halloran, Deirdre. "Attention Budgets …" / Halloran, Deirdre. "Noise, Focus …" (name repeated, no dash)

Chicago 18 author-date:

Halloran, Deirdre. 2020a. … / Halloran, Deirdre. 2020b. … and (Halloran 2020a, 104)

Why the year alone stops working

An author–date citation is a lookup key. (Halloran, 2020) promises that exactly one entry in the list starts with Halloran and 2020; the moment there are two, the key is ambiguous and every citation to either work is wrong. Author–page systems like MLA never used the year as the key, so they reach for the title instead. The three manuals therefore give three different answers to the same problem, and the letters that APA requires are a mistake in MLA.

The two works below are used throughout. Both are by one author, both appeared in 2020, and they sort as Attention before Noise. Change the titles and the letters may swap: the letter follows the title order, never the order in which you cited the works or the month they were published.

The two sources

Work 1:

Deirdre Halloran, "Attention Budgets in Open-Plan Offices," Journal of Workplace Psychology 14, no. 2 (2020): 101–118, https://doi.org/10.1000/jwp.2020.0142

Work 2:

Deirdre Halloran, "Noise, Focus, and the Four-Day Week," Journal of Workplace Psychology 14, no. 4 (2020): 355–372, https://doi.org/10.1000/jwp.2020.0144

APA 7: 2020a, 2020b

APA 7 §9.47 orders references with the same author and year alphabetically by title, ignoring A, An, and The, and then assigns lowercase letters after the year: 2020a, 2020b, 2020c. The letters are part of the date element, so they appear in the reference list and in every in-text citation. The only exception to title order is a set of works that belong to a numbered series, such as Part 1 and Part 2, which are ordered by series position. The APA Style references section and the citations section carry the official wording.

APA 7, reference list and in-text citations

References (title order):

Halloran, D. (2020a). Attention budgets in open-plan offices. Journal of Workplace Psychology, 14(2), 101–118. https://doi.org/10.1000/jwp.2020.0142

Halloran, D. (2020b). Noise, focus, and the four-day week. Journal of Workplace Psychology, 14(4), 355–372. https://doi.org/10.1000/jwp.2020.0144

Parenthetical, one work:

(Halloran, 2020a)

Narrative:

Halloran (2020b) found that …

Both works together:

(Halloran, 2020a, 2020b)

Quotation with a page:

(Halloran, 2020a, p. 104)

When you cite both works in one parenthetical, give the author once and the letters in order, separated by a comma. Do not write (Halloran, 2020a; Halloran, 2020b); the semicolon form is for different authors. Once a work has a letter, it keeps that letter everywhere in the paper, including the first citation, so assign the letters when you build the reference list and then cite from it. The in-text citation generator will accept 2020a in the year field.

Works with full dates keep the letter after the year

A blog post or newspaper article has a month and day in its reference, but the in-text citation uses the year only, so two 2020 posts by one author collide exactly as two articles do. Put the letter immediately after the year, before the comma and the month, and cite the year plus letter in the text. The works are still ordered by title, not by date.

APA 7, two dated posts in one year

References:

Halloran, D. (2020a, September 14). Meetings are not the problem. Harbor Labs Research. https://www.harborlabsresearch.org/blog/meetings-are-not-the-problem

Halloran, D. (2020b, March 2). What an interruption costs. Harbor Labs Research. https://www.harborlabsresearch.org/blog/what-an-interruption-costs

In-text:

(Halloran, 2020a); (Halloran, 2020b)

No date and in press: n.d.-a, in press-a

APA treats n.d. and in press as dates, so they can collide too. Add the letter after a hyphen: n.d.-a, n.d.-b, in press-a, in press-b. The hyphen exists because n.d.a would be unreadable; it is not used with a numeric year. The no-date guide shows a full pair of undated dictionary entries.

APA 7, undated and forthcoming pairs

References, no date:

Harbor Labs Research. (n.d.-a). Focus time policy. https://www.harborlabsresearch.org/policies/focus-time

Harbor Labs Research. (n.d.-b). Meeting-free Wednesdays. https://www.harborlabsresearch.org/policies/meeting-free-wednesdays

In-text, no date:

(Harbor Labs Research, n.d.-a); (Harbor Labs Research, n.d.-b)

References, in press:

Halloran, D. (in press-a). Attention and the open door. Journal of Workplace Psychology.

Halloran, D. (in press-b). Recovering focus after interruption. Occupational Health Quarterly.

In-text, in press:

(Halloran, in press-a, in press-b)

Where the pair sits in the full reference list

APA orders one author's solo works by year, earliest first, and letters only distinguish works within one year. A solo entry always precedes a co-authored entry that starts with the same surname, regardless of year, and co-authored entries are then ordered by the second author's surname. So Halloran's list runs: Halloran (2019), Halloran (2020a), Halloran (2020b), then Halloran & Mbeki (2018). The bibliography alphabetizer applies that order; the multiple-authors guide covers the co-author rules.

Not the same problem: same surname, different people

Letters are for one author with two works. If two different authors share a surname, APA distinguishes them with initials in the text, (D. Halloran, 2020) and (P. Halloran, 2020), and gives no letters. And if two multi-author works from the same year shorten to the same et al. form, APA adds authors until the citations differ, again with no letters. Check which situation you have before you reach for a and b.

MLA 9: shortened titles and three hyphens

MLA 9 does not use year letters. Its parenthetical is author–page, so when the list holds two works by one author the citation adds a shortened title after the author's name, followed by a comma between name and title and a space, not a comma, before the page. The works-cited list alphabetises the author's works by title and, from the second entry on, replaces the name with three hyphens and a period, ---., which the ninth edition retains. The MLA Style Center and the works-cited quick guide set the entry format.

MLA 9, works cited and in-text citations

Works cited (title order):

Halloran, Deirdre. "Attention Budgets in Open-Plan Offices." Journal of Workplace Psychology, vol. 14, no. 2, 2020, pp. 101–18, https://doi.org/10.1000/jwp.2020.0142.

---. "Noise, Focus, and the Four-Day Week." Journal of Workplace Psychology, vol. 14, no. 4, 2020, pp. 355–72, https://doi.org/10.1000/jwp.2020.0144.

Parenthetical:

(Halloran, "Attention Budgets" 104)

Author named in the sentence:

Halloran reports a measurable cost ("Noise, Focus" 360).

Author and title in the sentence:

In "Attention Budgets," Halloran reports a measurable cost (104).

Shorten the title to its first noun phrase and keep the formatting of the full title: quotation marks for an article, italics for a book, so (Halloran, *Long Quiet* 88) for a book and (Halloran, "Noise, Focus" 360) for an article. If two titles begin with the same words, extend the short form until they differ. Because the title does the work the year would do in APA, this rule applies whether the two works are from the same year or ten years apart; the MLA in-text guide covers the general form.

When the three hyphens may not be used

  • The name must be identical. The hyphens stand for exactly the author line above them. A work by Halloran and Mbeki gets its full names, Halloran, Deirdre, and Tomas Mbeki., because the author line is different.
  • A different role needs the role after the hyphens. If Halloran edited the second work, write ---, editor. rather than ---.
  • Solo before co-authored. All of Halloran's solo works come first, alphabetised by title; works with co-authors follow, alphabetised by the co-author's surname.
  • *Ignore A, An, and The*** when alphabetising titles, but keep them in the entry.
  • No year letters anywhere. (Halloran 2020a) is an APA habit that makes no sense in a list without dates as keys.

Chicago 18: repeat the name in bibliographies, letters in author-date

Chicago splits along its two systems. In notes-bibliography the note carries the title, so nothing extra is needed to tell the works apart; the only decision is how to list them. In author-date the year is the key, so Chicago borrows the same letters APA uses. Both systems are set out in the official Notes and Bibliography and Author-Date citation guides.

Notes-Bibliography

Under CMOS 16, a bibliography replaced a repeated author's name with a 3-em dash. CMOS 17 retired that recommendation and CMOS 18 keeps the change: repeat the author's name in full in every entry. The dash caused problems for sorting software, screen readers, and readers who landed mid-list, and repeating the name costs a few characters. Some publishers still apply the dash at typesetting; if yours does, that is a house decision, not a Chicago rule. An author's works are alphabetised by title within the bibliography, whatever their years.

Chicago 18 notes-bibliography

First note, work 1:

1. Deirdre Halloran, "Attention Budgets in Open-Plan Offices," Journal of Workplace Psychology 14, no. 2 (2020): 104, https://doi.org/10.1000/jwp.2020.0142.

First note, work 2:

2. Deirdre Halloran, "Noise, Focus, and the Four-Day Week," Journal of Workplace Psychology 14, no. 4 (2020): 360, https://doi.org/10.1000/jwp.2020.0144.

Shortened notes:

3. Halloran, "Attention Budgets," 106.

4. Halloran, "Noise, Focus," 362.

Bibliography (name repeated, title order):

Halloran, Deirdre. "Attention Budgets in Open-Plan Offices." Journal of Workplace Psychology 14, no. 2 (2020): 101–18. https://doi.org/10.1000/jwp.2020.0142.

Halloran, Deirdre. "Noise, Focus, and the Four-Day Week." Journal of Workplace Psychology 14, no. 4 (2020): 355–72. https://doi.org/10.1000/jwp.2020.0144.

Shortened notes are what make this system work: after the first full note, every later reference to a work is author plus shortened title plus page, so two works by one author are never confused. The same-source guide covers shortened notes and ibid., and the Chicago footnote generator produces both the full and short forms.

Author-Date

Chicago author-date lists one author's works chronologically, and works from the same year are alphabetised by title and given a, b, c after the year in both the reference list and the text. Unlike APA, Chicago puts no comma between author and year, so the text citation is (Halloran 2020a, 104). Citing both works together gives the author once and the year-letters separated by a comma: (Halloran 2020a, 2020b). The letter is attached to the year in the reference entry, where it follows the author's name.

Chicago 18 author-date

Reference list:

Halloran, Deirdre. 2020a. "Attention Budgets in Open-Plan Offices." Journal of Workplace Psychology 14 (2): 101–18. https://doi.org/10.1000/jwp.2020.0142.

Halloran, Deirdre. 2020b. "Noise, Focus, and the Four-Day Week." Journal of Workplace Psychology 14 (4): 355–72. https://doi.org/10.1000/jwp.2020.0144.

In-text, one work:

(Halloran 2020a, 104)

In-text, both works:

(Halloran 2020a, 2020b)

Narrative:

Halloran (2020b, 360) reports …

The name is repeated in author-date reference lists for the same reason it is repeated in bibliographies. Solo works precede co-authored works that begin with the same name, and co-authored works are then ordered alphabetically by the next author. Undated works in Chicago author-date take n.d. in the year slot; if two collide, distinguish them with letters after the abbreviation, following the same title order.

Three styles side by side

APA 7

Key:

Year plus letter: 2020a, 2020b

Order:

By title, ignoring A, An, The

List entry:

Name repeated; letter inside the date parentheses

In-text:

(Halloran, 2020a); (Halloran, 2020a, 2020b)

MLA 9

Key:

Shortened title

Order:

By title, ignoring A, An, The

List entry:

Name once, then ---. for each further solo work

In-text:

(Halloran, "Attention Budgets" 104)

Chicago 18

Key:

Notes: shortened title. Author-date: 2020a, 2020b

Order:

Bibliography: by title. Author-date: by year, then title

List entry:

Name repeated in full; no 3-em dash since CMOS 17

In-text:

Halloran, "Noise, Focus," 360. or (Halloran 2020a, 104)

Same author, same year: what changes in each style.
QuestionAPA 7MLA 9Chicago 18 notesChicago 18 author-date
Year letters?Yes, requiredNoNoYes, required
What decides a versus bTitle orderNot applicableNot applicableTitle order
Repeated name in the listRepeated--- from the second entryRepeatedRepeated
Two works in one citation(Halloran, 2020a, 2020b)(Halloran, "Attention Budgets" 104; "Noise, Focus" 360)Two shortened notes, or one note with both(Halloran 2020a, 2020b)
No daten.d.-a, n.d.-bOmit the date; titles distinguishTitles distinguishn.d., with letters if two collide
Forthcomingin press-a, in press-bforthcoming in the date slot; titles distinguishforthcoming; titles distinguishforthcoming; add letters only if two collide
Comma between author and yearYesNo year in the citationNo year in the citationNo

A short checklist

Before you submit a list with two works by one author

  • I confirmed the works are by the same author, not by two people who share a surname.
  • I sorted the works by title, ignoring A, An, and The.
  • APA and Chicago author-date: I put a, b, c after the year in the list and in every citation, including the first.
  • APA: I used n.d.-a and in press-a with a hyphen, and 2020a without one.
  • MLA: I added a shortened title in each parenthetical, with a comma after the name and none before the page, and I used ---. only for an identical author line.
  • Chicago: I repeated the name in each bibliography or reference-list entry instead of a 3-em dash.
  • I re-checked the letters after any late addition to the list, because a new title can change the order.

Common mistakes

  • Assigning a and b by the order you cited the works, or by the month they were published. The letters follow title order.
  • Using letters in the reference list but not in the text, or in the text but not in the list. Both places, every time.
  • Writing (Halloran, 2020a; Halloran, 2020b) in APA for two works by the same author. Give the name once: (Halloran, 2020a, 2020b).
  • Writing 2020-a or n.d.a. Numeric years take no hyphen; n.d. and in press do.
  • Adding year letters in MLA, or a comma before the page number in an MLA parenthetical with a title.
  • Using ---. in MLA for a co-authored work that follows a solo work. The author line differs, so the names are written out.
  • Using a 3-em dash in a Chicago bibliography because an older template did. CMOS 17 and 18 repeat the name.
  • Writing (Halloran, 2020a) in Chicago author-date. Chicago has no comma between author and year.
  • Forgetting to re-letter after adding a third 2020 work whose title sorts between the first two.

Sort the list, then letter it

Generate each entry as normal, then alphabetise the list so that same-author, same-year works fall into title order. Add the a and b letters in the year field for APA or Chicago author-date and let the in-text tool carry them into the citations; in MLA, the alphabetizer puts the works into the order the three hyphens depend on.

Bibliography alphabetizer →In-text citation generator →Journal article citation generator →

Frequently asked questions

How do I cite two works by the same author from the same year in APA?
Order the references alphabetically by title, ignoring A, An, and The, and add lowercase letters after the year: (2020a) and (2020b). Use the same letters in every in-text citation, for example (Halloran, 2020a). To cite both at once, write (Halloran, 2020a, 2020b) with the name given once.
How are the a and b letters assigned?
By the alphabetical order of the titles, not by publication month or by the order you cite the works in your paper. If a third work with a title that sorts between the first two is added later, the letters shift, so assign them from the finished reference list. Works that are parts of a numbered series are the one exception and take series order.
Does MLA use 2020a and 2020b?
No. MLA in-text citations are author–page, so two works by one author are distinguished by a shortened title after the author's name: (Halloran, "Attention Budgets" 104). In the works-cited list the entries are alphabetised by title and the second and later entries replace the author's name with three hyphens and a period.
What do the three hyphens mean in an MLA works-cited list?
They stand for exactly the same author line as the entry above, so the reader does not have to reread the name. They may be used only when the name is identical; a co-authored work following a solo work is written out in full, and a different role is added after the hyphens, as in ---, editor. MLA 9 retains this convention.
Does Chicago still use the 3-em dash for a repeated author?
Not as its recommendation. CMOS 17 replaced the dash with the repeated name, and CMOS 18 keeps that rule for bibliographies and author-date reference lists. Some publishers still insert the dash at typesetting, but a paper following Chicago repeats the author's full name in each entry.
How does Chicago author-date handle two works from one year?
The same way APA does, with a and b after the year, assigned in title order and used in both the reference list and the text. The punctuation differs: there is no comma between author and year, so the citation is (Halloran 2020a, 104), and both works together are (Halloran 2020a, 2020b).
What if the two works have no date, or are in press?
APA adds the letter after a hyphen: n.d.-a and n.d.-b, or in press-a and in press-b, ordered by title. MLA omits the date and relies on titles, so nothing changes. Chicago author-date writes n.d. in the year slot and adds letters only if two undated works by the same author collide.
Two different authors share a surname and both published in 2020. Do I use letters?
No. Letters are for one author with two works. For different people with the same surname, APA adds initials in the text, (D. Halloran, 2020) and (P. Halloran, 2020); MLA adds first names or initials in the same way; Chicago includes the first name in the note or the text citation where confusion is possible.