And then I found this on the second one down that list of "hits."
 
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cf.
 
And that brings us to this interesting little gem, which, used
correctly, does fill a need. But it is so widely misused that if you use
it, probably no one will know if you are using it correctly or if you
are using it in one of the many interesting alternate meanings
that have cropped up over the years. Cf. (note the one period) is short
for confer, which means compare, which means that
you are citing a contradictory reference. Think of it as meaning "but on
the other hand, see..." For example, if I believe that
Molly Malone died of a fever and Jones believes that she died of
something else, then I'm technically using cf. correctly when I
say:
 
     The evidence clearly indicates that Molly Malone died of a fever
(cf. Jones 1970).
 
But unfortunately, a lot of people are going to miss that subtlety. If
you want to use cf., you would be doing scholarship a favor
if you not only used it correctly, but used it in such a way that leaves
no doubt that you know how to use it correctly.
 
     The evidence clearly indicates that Molly Malone died of a fever,
though there are at least a few people who
     disagree with this conclusion (cf. Jones 1970).
 
(Frankly, I'm not sure what botanists and zoologists mean when they use
it with a genus and species, but they always seem to
know what they're doing and seem to do it consistently.)
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