intros a l H' q.
rewrite (H' q); auto.
Qed.
Let DescA := Desc (mon n) ltM.
Set Implicit Arguments.
Unset Strict Implicit.
Definition olist (p : list (Term A n)) := DescA (fP p).
Hint Resolve d_nil d_one.
Hint Unfold olist DescA.
Set Strict Implicit.
Unset Implicit Arguments.

Theorem olistOne : forall a b : Term A n, ltT b a -> olist (pX a (pX b pO)).
unfold olist, ltT in |- *; simpl in |- *; auto.