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 Th106:
  for w,p holds (p | (w | w)) | (w | p) = p
proof
  let w,p;
  (w | w) | p = p | (w | w) by Th83;
  hence thesis by Th97;
end;
