Proof using.
intros.
generalize (xelements_complete _ _ _ _ H); clear H; intros.
revert p0 H.
induction p; destruct p0; simpl; intros; eauto; try discriminate.
Qed.

Lemma xelements_bits_lt_2 : forall p p0 q m v,
List.In (p0,v) (xelements m (append p (xI q))) -> E.bits_lt p p0.