Placement of period in sentence that ends with "et al." followed by reference number? I have a citation that is at the end of a sentence with dual punctuation. What I mean is that I have a sentence of the following form:


  Blah blah blah is mentioned by Author et al.


What is the proper way to include the citation in this case?



  Blah blah blah is mentioned by Author et al[##].


  Blah blah blah is mentioned by Author et al.[##]


  Blah blah blah is mentioned by Author et al.[##].

Other
Since "et al." is an abbreviation of the latin et alii meaning "and others" the period in "et al." should be treated as periods in any other abbreviation such as "cf.", "Op. Cit.", "conf.", "c.". In most cases of which I am aware periods are shown after abbreviations but I am not a stranger to styles where the period after abbreviations are ignored. So my bet is that "et al. [##]." or "et al. [##]", depending on where the preferred location of the numbered references are, in a majority of cases. If you are uncertain you need to consult the journal style sheet (if any exists) or simply check other recent papers published by the journal in order to see how they prefer to have things set.