reserve U for Universe;
reserve x for Element of U;

theorem
  OddNAT is class of FinSETS
  proof
    now
      OddNAT c= NAT & omega c= FinSETS by CLASSES4:43;
      hence OddNAT c= FinSETS;
      thus OddNAT is denumerable by Th4;
    end;
    hence thesis by Th31;
  end;
