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

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)).