
theorem Th5:
  for L being upper-bounded Lattice holds not(ex b being Element of
  L st b is-upper-neighbour-of Top L)
proof
  let L be upper-bounded Lattice;
  given b being Element of L such that
A1: b is-upper-neighbour-of Top L;
A2: b [= Top L by LATTICES:19;
  Top L [= b & Top L <> b by A1;
  hence thesis by A2,LATTICES:8;
end;
