Apparently, this user prefers to keep an air of mystery about them.
12 Where, specifically, did Principia Mathematica fail? Aug 5 '13
5 Prove that at a party with at least two people, there are two people who know the same number of people… Jul 17 '13
2 Pigeonhole principle: show that a class of nine has at least five male or five female students. Jul 15 '13