reserve X for set;
reserve UN for Universe;

theorem Th77:
  GrothendieckUniverse omega = GrothendieckUniverse FinSETS = SETS
  proof
    GrothendieckUniverse omega = GrothendieckUniverse FinSETS
    proof
      GrothendieckUniverse omega = SETS by CLASSES3:22,Th75;
      hence thesis by CLASSES3:22;
    end;
    hence thesis by CLASSES3:22;
  end;
