Strong matching

Strong matching --- строгое паросочетание.

A strong matching is a matching [math]\displaystyle{ M = \{e_{1}, e_{2}, \ldots, e_{k}\} }[/math] where no end of [math]\displaystyle{ e_{i} }[/math] is adjacent to an end of [math]\displaystyle{ e_{j} }[/math], [math]\displaystyle{ 1 \leq i \neq j \leq k }[/math].