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 Th102:
  for w,p holds ((p | w) | ((w | w) | p)) = p
proof
  let w,p;
  w | p = p | w by Th83;
  hence thesis by Th92;
end;
