intros a b p q s H'; inversion_clear H'; intros.
absurd (ltT ltM a b); auto.
absurd (ltT ltM a b); auto.
absurd (ltT ltM a b); auto.
apply pX_inj; auto.
apply uniq_minusp with (l := (pX a p, q)); simpl in |- *; auto.
Qed.

Theorem minusP_inv3a :
forall (a b : Term A n) (p q s : list (Term A n)),
eqT a b ->
zeroP (A:=A) A0 eqA (n:=n) (minusTerm (A:=A) minusA (n:=n) a b) ->
minusP (pX a p) (pX b q) s -> s = minuspf p q.