I am preparing to give a presentation after few days. Some papers are authored by two people and some are by three. While referring their work during presentation what should I write for two authors.

Suppose there are two authors only - X and Y. Shall I write X et al. proved that ...... or X and Y proved that....

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    You say "write for two authors" but presentations involve speaking. So just to clarify, are you talking about what citation information to put on a slide? Jan 13, 2015 at 4:08
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    Follow a specific citation style (APA MLA ..etc) and put whatever it says
    – seteropere
    Jan 13, 2015 at 4:21
  • @JeromyAnglim yeah presentation involves speaking and using slides too.
    – monalisa
    Jan 13, 2015 at 4:22
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    @seteropere: I disagree. In fields in which author order is always alphabetical, "X et al." is rude and even discriminatory to those who happen to have names at the end of the alphabet. Assuming the list of all the authors' names fits on a single line, I see no reason not to include them all at least once. Jan 13, 2015 at 4:30
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    @PeteL.Clark nice perspective. Had no clue that this might look bad in some situations.
    – seteropere
    Jan 13, 2015 at 4:32

3 Answers 3


This was addressed on English.SE, Is "et al." acceptable for citations with exactly two authors?

The answers there indicate that major citation styles (MLA, Harvard) do not use "et al." when there are only two authors.

APA style also does not use "et al." for only two authors.

I'm not going to exhaustively check every citation style, but I'm not personally aware of any where "et al." is acceptable when citing a publication with only two authors.

Also of interest to those who happen to like grammar: the English.SE answer also points out that using "et al." for two authors can be considered incorrect, regardless of style considerations (text in brackets is added by me):

The Latinate abbreviation "et al." is short for "et alii," which means, "and others," and always refers to people, not objects. So if you had two authors, adding "et al." would indicate that there were [plural] other authors - and since there are no[t multiple] other authors in this case, it is incorrect to use it.

While "et al." could also technically stand for the singular "et alia" which would be technically correct, that's certainly not a conventional abbreviation.

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    +1. Obligatory nitpickery: et alia would be the correct singular only if the second author is female - if the second author is male, the correct form is et alius. SCNR. Jan 13, 2015 at 9:01

Follow the requirements of the journal, if they are firm. But let me argue why you should include all the authors, if possible, in many circumstances, even if there are three or four (or more). In particular, I come from a mathematics background, but this applies to many fields.

When you cite a paper as "X et al.,", the other author names are invisible. If the paper is good, and gets cited often in this way, people may begin to know it as the "X et al." paper - thus obscuring the contributions of the other authors. Thus X gets, in effect, sole credit in the text, and the other authors are relegated to the references section. The same holds at presentations.

Reputation is particularly important for many authors - especially younger ones, but even well established ones. It helps build their reputation for quality work, which in turn is related to jobs, grants, editorships, etc. The authors whose names are obscured may miss out on recognition that they actually deserve, solely so that an author can save a few characters in an electronic document.

This is particularly relevant in fields where authorships are alphabetical by default, such as mathematics. In this case, the first author only had the luck to have a name that comes earlier in the alphabet.

There have been studies where the effect of having an early-in-the-alphabet name have been investigated. Two of them are:

The essay "Et al." is unethical by Noah Snyder was influential in my thinking about this issue.

  • Yeah, I agree with you. thanks for the answer.
    – monalisa
    Jan 14, 2015 at 3:01

While in publications, you should follow whatever the official style is, in presentations you are typically much less constrained.

My own guiding principle for slides is to minimize the amount of visual clutter on screen, and especially to minimize text---after all, I want people to be listening to the talk, rather than simply reading the slides. What's important to communicate is:

  • This material belongs to a particular publication (either yours or somebody else's)
  • A sufficiently unique identifies that somebody can find it in an associated bibliography.

I go for a fairly sparse slide format, so I tend to communicate references in the tersest way possible on the slides, using [X & Y, YEAR] for 2 authors and [X et al., YEAR] for 3+, and then saying the citation more fully as I talk, e.g., "X, Y, and Z's paper last year in Annals of Randomology." In presentations, however, there is much space for personal style and expression. At the other extreme, I have also seen people include entire full citations on slides, complete with page numbers and DOI. What is important is to give credit while you can experiment with what best suits your own sense of design and the balance between communication and completeness.

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