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 Th92:
  for p,q holds p = (q | p) | ((q | q) | p)
proof
  let p,q;
  (q | q) | (q | q) = q by SHEFFER1:def 13;
  hence thesis by Th91;
end;
