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 Th133:
  for w,p holds (p | w) | (w | w) = w
proof
  let w,p;
  ((w | w) | (p | w)) = (p | w) | (w | w) by Th83;
  hence thesis by Th121;
end;
