reserve L for satisfying_Sh_1 non empty ShefferStr;

theorem Th38:
  for x, y, z being Element of L holds x | (y | (z | (x | y))) = x | (y | y)
proof
  let x, y, z be Element of L;
  set Y = z;
  y | (x | (y | (Y | (x | y)))) = y | y by Th34;
  hence thesis by Th27;
end;
