 reserve L for AD_Lattice;
 reserve x,y,z for Element of L;
 reserve L for GAD_Lattice;
 reserve x,y,z for Element of L;

theorem  :: Theorem 3.7. (1) <=> (3)
  (x "/\" y) "\/" x = x iff (y "/\" x) "\/" y = y by Th3713;
