How should multiple Harvard references with same first author but different coauthors be made? This question was written by a friend of mine. I'm helping them by posting it here, with permission.
How should I use the name-year referencing system (loosely speaking, the Harvard system) in such cases where there are multiple works that have the same first author but a different set of coauthors?
In such cases where the maximum number of authors among all articles sharing the same first author is not more than three, or perhaps four, the solution is very simple. Just mention them all inline and use the reference list as usual. E.g. the following:

&quot;... the complex formation was observed by Miller and Nelson (1991)&quot;
&quot;... cf. Miller, Nelson and Byrne (1993)&quot;

However, if there are more authors in any of the articles, this gets quite tricky, since listing a huge number of authors inline is definitely not an option to me. I'd rather change to number references.
Now, making the references unambiguous is not a problem. For instance, the following references could be addressed to inline as &quot;Barton et al.&quot; without in any way losing the one-to-one relation between inline citations and reference list entries. That is, the articles are differentiated, as the other is &quot;Barton et al. (1980)&quot; and the other &quot;Barton et al. (1985)&quot;.

Barton, D. H. R.; Crich, D.; Potier, P. (1985). &quot;On the mechanism of the decarboxylative rearrangement of thiohydroxamic esters&quot;. Tetrahedron Lett. 26, 5943.
Barton, D. H. R.; Dowlatshahi, H. A.; Motherwell, W. B.; Villemin, D. V. (1980). &quot;A New Radical Decarboxylation Reaction for the Conversion of Carboxylic Acids into Hydrocarbons&quot;. J. Chem. Soc. Chem. Commun., p. 732.

What really is the problem is the alphabetical order in which the references should be sorted in the reference list. If the articles listed above are referred to just as &quot;Barton et al.&quot;, the reader does not know the exact position in the reference list where to find the articles.
One solution might be just ignoring this slight complication.
Other solution is to use &quot;et al&quot; in the reference list, too, if absolutely necessary. Thus, in the example above, the first article would be referred to as &quot;Barton, Crich and Potier (1985)&quot; inline, and the latter as &quot;Barton et al. (1980)&quot;.
In the reference list, they would be expressed and arranged according to the inline cites:

Barton, D. H. R.; Crich, D.; Potier, P. (1985). &quot;On the mechanism of the decarboxylative rearrangement of thiohydroxamic esters&quot;. Tetrahedron Lett. 26, 5943.
Barton, D. H. R. et al. (1980). &quot;A New Radical Decarboxylation Reaction for the Conversion of Carboxylic Acids into Hydrocarbons&quot;. J. Chem. Soc. Chem. Commun., p. 732.

Any other recommendations?
Please don't suggest Google, since I did not find an answer after 30 minutes of search. There are perhaps hundreds of &quot;Harvard citation guides&quot; available, but I found none that addressed this problem.
As eykanal said, journals usually provide their own formatting, and personally, I use latex/bibtex, so I tend to assume this kind of problems will be solved automatically.
That being said, in the case you describe, I would expect the ordering to be (first name, year), and in the case where there are multiple references with the same first author for the same year, then to use (Barton et al., 1980a) (Barton et al. 1980b). So your example would be:

Barton, D. H. R.; Dowlatshahi, H. A.; Motherwell, W. B.; Villemin, D. V. (1980). &quot;A New Radical Decarboxylation Reaction for the Conversion of Carboxylic Acids into Hydrocarbons&quot;. J. Chem. Soc. Chem. Commun., p. 732.
Barton, D. H. R.; Crich, D.; Potier, P. (1985). &quot;On the mechanism of the decarboxylative rearrangement of thiohydroxamic esters&quot;. Tetrahedron Lett. 26, 5943.

and the two references (Barton et al. 1980) and (Barton et al. 1985). That way, when I know I need to look first for the first name, and then to the year. Now, if let's assume that there is another reference by Barton and Alice in 1980, then you would have:

Barton, D. H. R.; Alice (1980a). &quot;Bla bla&quot;, p2.
Barton, D. H. R.; Dowlatshahi, H. A.; Motherwell, W. B.; Villemin, D. V. (1980b). &quot;A New Radical Decarboxylation Reaction for the Conversion of Carboxylic Acids into Hydrocarbons&quot;. J. Chem. Soc. Chem. Commun., p. 732.
Barton, D. H. R.; Crich, D.; Potier, P. (1985). &quot;On the mechanism of the decarboxylative rearrangement of thiohydroxamic esters&quot;. Tetrahedron Lett. 26, 5943.

and the references would be (Barton et al., 1980a) and (Barton et al., 1980b).
As for the question whether you should put the one with Alice first or second, it does not really matter, since the reference is unique anyway, but in this case, I would go for the month of publication if you have it, otherwise with the alphabetical order of the second author (and of the third one if the first two authors are the same, and so on).