Amusingly enough, it's personal communication with one of his students.
I believe it was his thesis and I assume it was tongue in cheek.
Realistically, the proof would probably just be rewritten in a paper in standard notation, with an indication that the original proof (or the idea) was due to an anonymous author. You see very similar things happen from…
Bill Thurston cited personal communication with himself, which is a pretty unusual source.
Amusingly enough, it's personal communication with one of his students.
I believe it was his thesis and I assume it was tongue in cheek.
Realistically, the proof would probably just be rewritten in a paper in standard notation, with an indication that the original proof (or the idea) was due to an anonymous author. You see very similar things happen from…
Bill Thurston cited personal communication with himself, which is a pretty unusual source.