Petersen graph is not a Cayley graph
10930
Why is the Petersen graph no Cayley graph?
125668
A proof that BS(1,2) is not polycyclic
99781
Proof that any simple connected graph has at least 2 non-cut vertices.
85018
When is the automorphism group of the Cayley graph of $G$ just $G$?
4112
How to prove that a simple graph having 11 or more vertices or its complement is not planar?
38466
Proving that the number of vertices of odd degree in any graph G is even
126927
$\mathbb Q$ is not the direct product of two non-trivial groups.
146386
Is there a reason why the number of non-isomorphic graphs with $v=4$ is odd?
71154
Why a complete graph has $\frac{n(n-1)}{2}$ edges?
102622
K is a subgroup of G. Show that K is not a normal subgroup
142861
Multipartite graphs which are not planar
17086
The number of (non-equal) forests on the vertex set V = {1, 2, ...,n} that contains exactly 2 connected components is given by
18383
List of ways to tell if degree sequence is impossible for a simple graph
67383
Prove that $G'$ is not planar.
44563
Weakly Connected Graphs
14447
Direct proof that $\pi$ is not constructible
156679
$K[X,Y]/(XY-1)$ not isomorphic to $K[T]$