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 Th125:
  for x,z,y holds (x | ((y | y) | z)) | z = z | (y | x)
proof
  let x,z,y;
  (z | z) | ((y | y) | z) = z by Th121;
  hence thesis by Th100;
end;
