elim H; intros.
rewrite H0; rewrite H1.
auto.
Qed.

(* Specifications: *)
Lemma NotInDOMIsUndef2 :
forall (s : SFSstate) (o1 o2 : OBJECT),
~ set_In o1 (domsecmat (secmat s)) ->
o1 = o2 -> None = fsecmat (secmat s) o2.
Lemma ChsubscPSS1 :
forall (s : SFSstate) (u : SUBJECT) (y : ReadersWriters),
(forall rw : ReadersWriters,
~ set_In u (ActReaders rw) /\ ~ set_In u (ActWriters rw)) ->
~ (set_In u (ActReaders y) \/ set_In u (ActWriters y)).