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 Th142:
  for z,q,y,x holds q | (x | z) = (z | ((x | (y | (y | y))) | q))
  | ((q | q) | ((x | (y | (y | y))) | q))
proof
  now
    let p,z,q,y,x;
    (z | z) | (p | (p | p)) = z by Th71;
    hence
    (q | (x | z)) = ((z | ((x | (y | (y | y))) | q)) | ((q | q) | ((x | (
    y | (y | y))) | q))) by Th141;
  end;
  hence thesis;
end;
