2-Section graph

[math]\displaystyle{ 2 }[/math]-Section graph --- [math]\displaystyle{ 2 }[/math]-секционный граф.

The [math]\displaystyle{ 2 }[/math]-section graph [math]\displaystyle{ 2SEC({\mathcal H}) }[/math] of the hypergraph [math]\displaystyle{ {\mathcal H} }[/math] has the vertex set [math]\displaystyle{ V }[/math] of this hypergraph, and two distinct vertices are adjacent if and only if they are contained in a common edge of [math]\displaystyle{ {\mathcal H} }[/math].