# AGSM bibliography style sometimes doesn't abbreviate to “et al.” for duplicate author+year

With BibTeX and the harvard/AGSM style, some references (from authors who have multiple papers per year) aren't abbreviated to "et al.", with the addition of a, b, et cetera. For example, with the code attached below, I get:

Only one paper is abbreviated to et al., the others not. Any idea why this is happening? The in-text references should be Basu et al. (2008a) and Basu et al. (2008b), which I believe AGSM should automatically do?

\documentclass[10pt,a4paper]{article}
\usepackage{natbib}

\begin{document}

\cite{basu2008a, basu2008b, beare2006}

\bibliographystyle{agsm}
\bibliography{references.bib}

\end{document}


With BibTeX file (references.bib):

@string{jam="J. Appl. Meteor."}
@string{ag="Acta Geop."}
@string{blm="Bound.-Layer Meteor."}

@article{basu2008a,
author={Basu, S. and Vinuesa, J.-F. and Swift, A.},
title={Dynamic {LES} modeling of a diurnal cycle},
journal=jam,
year={2008},
volume={47},
number={4},
pages={1156-1174}
}

@article{basu2008b,
author={Basu, S. and Holtslag, A. A. M. and Wiel, B. J. H. and Moene, A. F. and Steeneveld, G. J.},
title={An inconvenient "truth" about using sensible heat flux as a surface boundary condition in models under stably stratified regimes},
year={2008},
journal=ag,
volume={56},
number={1},
pages={88-99}
}

@ARTICLE{beare2006,
author={Beare,R. J. and Macvean,M. K. and Holtslag,A. A. M. and Cuxart,J. and Esau,I. and Golaz,J. -. and Jimenez,M. A. and Khairoutdinov,M. and Kosovic,B. and Lewellen,D. and Lund,T. S. and Lundquist,J. K. and McCabe,A. and Moene,A. F. and Noh,Y. and Raasch,S. and Sullivan,P.},
title={An intercomparison of large-eddy simulations of the stable boundary layer},
journal=blm,
year={2006},
volume={118},
number={2},
pages={247-272}
}

• It actually works correctly if both papers (basu2008a, basu2008b) have the exact same authors (result: Basu et al. (2008a,b)), or if one of the papers only has one author (result: Basu et al. (2008), Basu (2008)) or two authors (result; Basu et al. (2008), Basu & Holtslag (2008)). But as soon as it needs to add the a or b, something fails and the full list of authors is writting in-text – Bart Mar 4 '16 at 10:59
• This link may be helpful: tex.stackexchange.com/questions/26575/… – mirkom Mar 12 '16 at 11:29
• meanwhile also posted on latex-community.org/forum/viewtopic.php?f=50&t=27226 – Johannes_B Mar 14 '16 at 16:22
• @Johannes_B - Done. :-) It turns out that this is a feature, not a bug... For sure, a very uncommon feature. – Mico Mar 14 '16 at 20:30

You've come across an unusual -- and admittedly rather severely under-documented -- feature (not a bug...) of the agsm bibliography style. Suppose two bib items labelled, say, AA and BB each have one or more authors. Crucially, suppose the total number of authors differs -- e.g., let bibitem AA have 3 authors and bibitem BB have 5 authors -- and suppose further that AA and BB share the same first author (say, XYZ) and the same publication year (say, 2000).

When this occurs -- as is the case in the example you've posted -- the agsm bibliography style does not set the citation call-outs as XYZ et al (2000a) and XYZ et al. (2000b), respectively. Instead, it lists all author names for both publications.

I suppose this is a fail-safe way of avoiding any kind of confusion over whose publication might be cited as XYZ et al. (2000a).

The only time when you do get the FirstAuthor et al (year) citation call-out pattern is if (a) the two publications have the same authors (and thus the same number of authors) as well as the same publication year and (b) there is no other three-or-more-author publication in the bibliography that features the same first author and publication year.

Again, this feature of the agsm style is both uncommon (to put it neutrally) and, unfortunately, quite obscure and under-documented. I wouldn't call it a bug, though. If you truly can't stand this feature, it's probably a good idea to start looking for an alternative bibliography style.

An MWE and screenshot:

\RequirePackage{filecontents}
\begin{filecontents}{testagsm.bib}
@article{1,
author = "XYZ", title = "x", journal= "y", year = 2000}
@article{2,
author = "XYZ and B", title = "x", journal= "y", year = 2000}
@article{3a,
author = "XYZ and B and C", title = "x1", journal = "y", year = 2000}
@article{3b,
author = "XYZ and B and C", title = "x2", journal = "y", year = 2000}
@article{4,
author = "XYZ and BB and CC and DD", title = "x", journal= "y", year = 2000}
@article{5,
author = "XYZ and BBB and CCC and DDD and EEE", title = "x", journal= "y", year = 2000}
@article{x1,
author = "A and B and C", title = "D1", journal = "E1",
year = 3001, volume = 1, number = 2, pages = "3-4"}
@article{x2,
author = "A and B and C", title = "D2", journal = "E2",
year = 3001, volume = 5, number = 6, pages = "7-8"}
\end{filecontents}

\documentclass{article}
\usepackage{natbib,har2nat}
\bibliographystyle{agsm}
\setlength\parindent{0pt} % just for this example

\begin{document}
\begingroup
\obeylines
\citet{1}
\citet{2}
\citet{3a}, \citet{3b}
\citet{4}
\citet{5}

\medskip
\citet{x1}, \citet{x2}
\endgroup

\bibliography{testagsm}
\end{document}

• Well, that's indeed a very strange "feature" :) But awesome, thanks for looking into it. After a quick test, apalike seems to do what I want, so I'll give that a try. – Bart Mar 14 '16 at 20:46
• @Bart - Thanks for letting me know that you found this answer useful. About the apalike bibliography style: It's been around, virtually unchanged, since 1988. As such, it doesn't know what to do with (and hence ignores) fields such as url, eid, issn, etc. If such fields might be important for your thesis, and especially if your bibliography has to be formatted according to current (not 1988...) APA guidelines, you may want to look into using the much newer (and more feature-rich) apacite package and bibliography style. – Mico Mar 14 '16 at 21:04
• @Mico, again thanks...! The DOI's etc. were indeed missing, using apacite fixed that. – Bart Mar 14 '16 at 23:11

It is not a useful "feature" at all in any scientific writing I have seen. I have the problem where I have the same group of authors who published several works in one year. The workaround I use is to also change the year={} field in my reference.bib file to read "2008a", "2008b" and so on. Using the example above it would look like this:

@article{basu2008a,
author={Basu, S. and Vinuesa, J.-F. and Swift, A.},
title={Something},
journal=jam,
year={2008a},
volume={47},
number={4},
pages={1156-1174}
}

@article{basu2008b,
author={Basu, S. and Vinuesa, J.-F. and Swift, A.},
title={Something else},
year={2008b},
journal=ag,
volume={56},
number={1},
pages={88-99}
}


And so on ... then running BibTeX I get "Basu (2008ab)" as expected.

• But then you manually add year={2008a}, year={2008b}, etc., and what if you later remove (lets say) the one with 2008a? You manually have to update other references; isn't that what a reference manager should do for you? – Bart Dec 3 '18 at 14:50
• P.s.: what do you mean with Basu (2008ab)? That should never happen? – Bart Dec 3 '18 at 14:54
• You are correct - I should have written "Basu et al. (2008a,b)" – sea89 Dec 3 '18 at 14:57
• If I just use year = {2008}, in your .bib examples and add them to Mico's MWE I get the output "Basu et al. (2008a,b)" which seems really sensible. It goes against the spirit of BibTeX to add the a and b in the year field manually, since that letter might change or disappear when you add or remove other references. – moewe Dec 3 '18 at 16:33

By the way: I've made an interesting finding. If you are writing your authors in the .bib file twice into brackets it's also going to name all authors for the \citep{}.

Example: [...] author = {[Sheng, Steve and Holbrook, Mandy and Kumaraguru, Ponnurangam and Cranor, Lorrie Faith and Downs, Julie}}, [...]

For me this resulted in naming all authors in the citation.