
theorem Th20:
  for L being Boolean distributive' Lattice-like non empty
  LattStr holds Top L = Top' L
proof
  let L be Boolean distributive' Lattice-like non empty LattStr;
  set Y = Top L;
  L is upper-bounded' & for a being Element of L holds Y "/\" a = a & a
  "/\" Y = a by Th13;
  hence thesis by Def2;
end;
