theorem Th61:
  o1 = (the L_join of L)||P & o2 = (the L_meet of L)||P implies o1
is commutative & o1 is associative & o2 is commutative & o2 is associative & o1
  absorbs o2 & o2 absorbs o1 by Th1,Th5,LATTICE2:26,27;
