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 Th119:
  for p,x holds p | (x | p) = (x | x) | p
proof
  now
    let q,p,x;
    (((p | (x | p)) | (p | (x | p))) | (q | (q | q))) = (p | (x | p)) by Th71;
    hence p | (x | p) = (x | x) | p by Th118;
  end;
  hence thesis;
end;
