 reserve o,o1,o2 for object;
 reserve n for Ordinal;
 reserve R,L for non degenerated comRing;
 reserve b for bag of 1;

theorem
   for R holds BSFSeri(R) is RingIsomorphism &
   Formal-Series R is (Formal-Series(1,R))-isomorphic
   proof
     let R;
     BSFSeri(R) is RingHomomorphism & BSFSeri(R) is isomorphism;
     hence thesis by RING_3:def 4;
   end;
