intros l a b H'; split; auto.
apply olist_imp_olist with (b := b); auto.
inversion H'.
generalize H0; simpl in |- *; intuition.
Qed.

(* Specifications: *)
Theorem canonical_pX_ltP : forall a p, canonical (pX a p) -> ltP p (pX a pO).
intros a p H'; auto.