
theorem
  for L be upper-bounded non empty antisymmetric RelStr for a be Element
  of L holds Top L <= a implies a = Top L
proof
  let L be upper-bounded non empty antisymmetric RelStr;
  let a be Element of L;
A1: a <= Top L by YELLOW_0:45;
  assume Top L <= a;
  hence thesis by A1,YELLOW_0:def 3;
end;
