Please take a look at the comments related to this question. Dietrich Burde posted a comment which, in my opinion, should be an answer, be he thinks that perhaps the moderators will see it as a trivial answer. What do you think?
However, I think that we are a lot more lax about that here.
My general inclination is not to delete comments which provide answers (as, indeed, my general philosophy is not to delete too many comments; note that moving long threads to chat is not deletion).
I would further argue that the comment posted there is a reference plus an epsilon of commentary, and would need to fleshed out some to be a real answer.
