 reserve L for non empty LattStr;
 reserve v100,v102,v2,v1,v0,v3,v101 for Element of L;
 reserve L for WA_Lattice;
 reserve x,y,z,u for Element of L;

theorem
  ex z st x [= z & y [= z &
    for u st x [= u & y [= u holds z [= u
  proof
    take z = x "\/" y;
    thus thesis by Lemacik1,LemmaSum;
  end;
