
theorem Th67:
  for G1 being _Graph, G2 being G1-isomorphic _Graph
  for G3 being LGraphComplement of G1, G4 being LGraphComplement of G2
  holds G4 is G3-isomorphic
proof
  let G1 be _Graph, G2 be G1-isomorphic _Graph;
  let G3 be LGraphComplement of G1, G4 be LGraphComplement of G2;
  set G5 = the removeParallelEdges of G1;
  set G6 = the removeParallelEdges of G2;
  G6 is G5-isomorphic by GLIB_010:168;
  hence thesis by Th66;
end;
