During various travels, I encountered the following page on Wikipedia:
http://en.wikipedia.org/wiki/Folner_sequence
The proof in the "Proof of amenability" section is kind of neat and I'd like to incorporate it into some background material because it's easy to appreciate, but it doesn't appear (at least, as far as I can tell) in the one and only one referenced paper (Folner, 1955). The other books, papers, etc I have all talk in the language of means.
Does somebody have a source for this? Or is it a "made-nice-for-Wikipedia" restatement of some result I failed to appreciate in the paper?