
theorem Th89:
  for F1, F2 being non empty Graph-yielding Function st F1, F2 are_isomorphic
  holds canGFDistinction(F1),canGFDistinction(F2) are_isomorphic
proof
  let F1, F2 be non empty Graph-yielding Function;
  assume A1: F1,F2 are_isomorphic;
  canGFDistinction(F1),F1 are_isomorphic by Th42, Th87;
  then A2: canGFDistinction(F1),F2 are_isomorphic by A1, Th41;
  F2,canGFDistinction(F2) are_isomorphic by Th42, Th87;
  hence thesis by A2, Th41;
end;
