reserve m for Cardinal,
  A,B,C for Ordinal,
  x,y,z,X,Y,Z,W for set,
  f for Function;
reserve f,g for Function,
  L for Sequence,
  F for Cardinal-Function;
reserve U1,U2,U for Universe;

theorem
  U1 \/ U2 is Universe & U1 /\ U2 is Universe
proof
  U1,U2 are_c=-comparable by Th54;
  then U1 c= U2 or U2 c= U1;
  hence thesis by XBOOLE_1:12,28;
end;
