FEEDBACK VERTEX SET ON PLANAR GRAPHS
Hongbin Chen, Hung‐Lin Fu, Chie-Huai Shih · Taiwanese Journal of Mathematics · 2012
A feedback vertex set of a graph is a set of vertices whose removal results an acyclic graph. This paper shows that for every planar graph the minimum cardinality of a feedback vertex set is at most three times the maximum number of vertex disjoint cycles in the graph.