intros a p H' H'0 H'1; split; auto.
apply ltP_pX_olist; auto.
inversion H'.
generalize H0 H'0; simpl in |- *; case (zeroP_dec A A0 eqA eqA_dec n a); auto.
Qed.

Theorem not_double_canonical :
forall (a : Term A n) (p : list (Term A n)), ~ canonical (pX a (pX a p)).