theorem Th16:
  (for v holds u "/\" v = v) implies u = Top L
proof
  assume
A1: u "/\" v = v;
  now
    let v;
    v "/\" u = v by A1;
    then v [= u by LATTICES:4;
    hence u = v "\/" u;
  end;
  hence thesis by RLSUB_2:65;
end;
