As already mentioned...

[nyggus]

Hi: Suppose I am writing a paper. When I want to refer to something that has already been said in the paper, should I write
1. "As we have already mentioned,..." or
2. "As already mentioned,..." or
3. "As mentioned earlier,..." or maybe
4. "As mentioned before,..."?
The most important is a choice between the first two; I would choose the first one, for grammatical reasons, but I suppose that both are equally correct. The second one wins in Google Scholar, but it may be applied in some other situations.

Thansk & Best,
Nyggus

[Coffa]

"As already mentioned..." is the most natural, in formal writing. "As we have already mentioned..." is too stilted in my opinion. To me, it would instantly indicate an ESL/EFL writer, unless it were used specifically to indicate particular emphasis of a point.