reserve G for _Graph;

theorem Th64:
  for G1, G2 being _Graph holds G1 is Supergraph of G2 iff G2 c= G1
proof
  let G1, G2 be _Graph;
  G1 is Supergraph of G2 iff G2 is Subgraph of G1 by Th61;
  hence thesis by GLIB_000:def 35;
end;
