Graph union

Graph union --- объединение графов.

A graph union [math]\displaystyle{ G_{1} \cup G_{2} }[/math] of the graphs [math]\displaystyle{ G_{1} }[/math] and [math]\displaystyle{ G_{2} }[/math] is a graph with vertices in [math]\displaystyle{ V(G_{1}) \cup V(G_{2}) }[/math] and edges in [math]\displaystyle{ E(G_{1}) \cup E(G_{2}) }[/math].