Minor of a graph

Minor of a graph --- минор графа.

A graph $H$ obtained from $G$ by a series of vertex deletions, edge deletions and contractions of an edge. A class of graphs ${\mathcal F}$ is called minor-closed if for every graph $G$ in ${\mathcal F}$, every minor of $G$ is also a member of ${\mathcal F}$. For a class of graphs ${\mathcal F}$, a finite obstruction set $S$ is a finite set of minors such that a graph is a member of ${\mathcal F}$ if and only if it does not contain an element of $S$ as a minor.

The graphs in every minor-closed class of graphs are recognizable in ${\mathcal O}(n^{3})$ time.