reserve L for satisfying_Sh_1 non empty ShefferStr;
reserve L for satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3
  non empty ShefferStr;
reserve v,q,p,w,z,y,x for Element of L;

theorem Th152:
  for z,p,x holds z | (x | p) = z | (p | x)
proof
  now
    let y,z,p,x;
    (x | (y | (y | y))) | (x | (y | (y | y))) = x by Th136;
    hence z | (x | p) = z | (p | x) by Th151;
  end;
  hence thesis;
end;
