Apparently, this user prefers to keep an air of mystery about them.
8 How to prove that a simple graph having 11 or more vertices or its complement is not planar? Apr 6 '12
3 How to prove it by means of a combinatorial argument?(A combinatorial exercise) [duplicate] Mar 31 '12
1 A tree that does not satisfy: If $v$ and $w$ are vertices in $T$, there is a unique path from $v$ to $w$? Apr 7 '12