elim (in_wf l p n H2 H);intros.
generalize (factor_divides_refactor (p,n) l H2);simpl;intro.
rewrite H1 in H5.
assert (divides (refactor l') p).
apply divides_trans with (power p n);[trivial | apply power_divides_lemma1;auto with arith].
elim (prime_divides_refactor p l' H3 H0 H6);intro m;intro.
cut (n=m).
intro;rewrite H8;trivial.
apply le_antisym.
eapply prime_power_divides_refactor;eauto.
generalize (factor_divides_refactor (p,m) l' H7);simpl;intro.
rewrite <- H1 in H8.
apply prime_power_divides_refactor with p l;auto.
elim (in_wf l' p m);trivial.
Qed.

Lemma pwd_impl_set : forall (l:list (nat*nat)),(is_pwd l)->(is_set (nat*nat) l).
induction 1;[apply nil_is_set | apply cons_is_set;auto].