reserve G for _Graph;

theorem Th66:
  for G3 being _Graph, G2 being Supergraph of G3, G1 being Supergraph of G2
  holds G1 is Supergraph of G3
proof
  let G3 be _Graph, G2 be Supergraph of G3, G1 be Supergraph of G2;
  G3 is Subgraph of G2 & G2 is Subgraph of G1 by Th61;
  then G3 is Subgraph of G1 by GLIB_000:43;
  hence thesis by Th61;
end;
