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 Th107:
  for p,w holds (w | p) | (w | (p | p)) = w
proof
  let p,w;
  (p | p) | w = w | (p | p) by Th83;
  hence thesis by Th102;
end;
