## Graph minors

- N. Robertson, P. Seymour
- XX. Wagner’s conjecture. J. Comb. Theory Ser. B…
- 2004

The class of outerplanar graphs is minor-closed and can be characterized by two excluded minors: K4 and K2,3. The class of graphs that contain a vertex whose removal leaves an outerplanar graph is also minor-closed. We provide the complete list of 57 excluded minors for this class.