Orthogonal double cover

Orthogonal double cover --- ортогональное двойное покрытие.

An orthogonal double cover of a complete graph [math]\displaystyle{ K }[/math] by a graph [math]\displaystyle{ G }[/math] is a set of subgraphs of [math]\displaystyle{ K }[/math] each isomorphic to [math]\displaystyle{ G }[/math], such that every edge of [math]\displaystyle{ K }[/math] is contained in exactly two subgraphs and each two subgraphs have exactly one edge in common.