reserve L for satisfying_Sh_1 non empty ShefferStr;

theorem Th47:
  for x, y, z being Element of L holds x | ((y | y) | (z | (x | (x
  | y)))) = x | ((y | y) | (y | y))
proof
  let x, y, z be Element of L;
  x | (y | y) = x | (x | y) by Th44;
  hence thesis by Th38;
end;
