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 Th149:
  for p,z,y,x holds (((z | (x | p)) | (z | (x | p))) | (((x | (y
| (y | y))) | z) | ((p | p) | z))) = ((((p | p) | z) | ((x | (y | (y | y))) | z
  )) | (((p | p) | z) | ((x | (y | (y | y))) | z)))
proof
  let p,z,y,x;
  (((x | (y | (y | y))) | z) | ((p | p) | z)) = ((z | (x | p)) | (z | (x |
  p))) by Th73;
  hence thesis by Th87;
end;
