The Oxford Guide to Style (pp.574-5) tells us that: "The abbreviation cf. (confer 'compare') is used to signal that one item is to be compared with another elsewhere....Do no confuse 'cf.' with 'see', which has a broader purpose".
Sussex university tells us in its Style Guide: "[...] very many people who should know better use the Latin abbreviation cf., which properly means `compare', merely to refer to published work. It is now very common to see something like this:
*The Australian language Dyirbal has a remarkable gender system; cf. Dixon (1972).
This is quite wrong, since the writer is not inviting the reader to compare Dixon's work with anything, but only to consult that work for more information. Hence the correct form is this:
The Australian language Dyirbal has a remarkable gender system; see Dixon (1972)."http://www.informatics.sussex.ac.uk/departmen...
Therefore, cf. tells us that what is in the text should be compared to something in another work; i.e. the two are quite possible different.
Now, I understand "vgl." to mean "ein Verweis auf eine nicht wortwörtlich, sondern umschrieben zitierte Stelle aus einer Informationsquelle" (http://de.wiktionary.org/wiki/vgl
. -- OK, wiki dictionary is not the most reliable of sources, but I would be interested to know if I understand it correctly).
For me, cf. and vgl. (assuming that I have understood the later correctly) actually have almost opposite meanings. It therefore strikes me as an incorrect translation.