theorem Th141:
  for z,p,q,y,x holds q | (x | z) = (((z | z) | (p | (p | p))) |
  ((x | (y | (y | y))) | q)) | ((q | q) | ((x | (y | (y | y))) | q))
proof
  let z,p,q,y,x;
  ((((x | (y | (y | y))) | q) | ((z | z) | q)) | ((q | (x | z)) | (q | (x
  | z)))) = (q | (x | z)) by Th139;
  hence thesis by Th140;
end;
