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 Th127:
  for z,y,x holds y = (((x | x) | x) | y) | ((z | z) | y)
proof
  now
    let x,y,z,p;
    ((y | (((p | (p | p)) | (p | (p | p))) | z)) | (y | (((p | (p | p)) |
    (p | (p | p))) | z))) = y by Th124;
    hence y = (((x | x) | x) | y) | ((z | z) | y) by Th110;
  end;
  hence thesis;
end;
