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 Th150:
  for p,z,y,x holds (z | (x | p)) = ((((p | p) | z) | ((x | (y |
  (y | y))) | z)) | (((p | p) | z) | ((x | (y | (y | y))) | z)))
proof
  let p,z,y,x;
  (((z | (x | p)) | (z | (x | p))) | (((x | (y | (y | y))) | z) | ((p | p)
  | z))) = z | (x | p) by Th144;
  hence thesis by Th149;
end;
