
theorem Th13:
  for L being Boolean Lattice-like non empty LattStr holds L is
  upper-bounded'
proof
  let L be Boolean Lattice-like non empty LattStr;
  ex c being Element of L st for a being Element of L holds c "/\" a = a &
  a "/\" c = a
  proof
    take c = Top L;
    let a be Element of L;
    thus thesis;
  end;
  hence thesis;
end;
