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 Th105:
  for p,w holds (w | p) | (p | (w | w)) = p
proof
  let p,w;
  (w | w) | p = p | (w | w) by Th83;
  hence thesis by Th92;
end;
