reserve L for Lattice;
reserve X,Y,Z,V for Element of L;
reserve L for D_Lattice;
reserve X,Y,Z for Element of L;
reserve L for 0_Lattice;
reserve X,Y,Z for Element of L;

theorem Th11:
  X "\/" Y = Bottom L iff X = Bottom L & Y = Bottom L
by LATTICES:5,LATTICES:16;
