One of the highlights in the Robertson-Seymour theory on graph minors is the finiteness (for each fixed surface S) of the set of the minimal forbidden minors for S. Theorem 7.0.1 (Robertson and ...
If true, the following conjecture of Thomassen [Th81] is a planarity criterion for a special class of graphs that involves only K 5. Recall that a planar graph on n vertices contains at most 3n-6 ...