intros P Q H' a b H'0; inversion H'0; auto.
apply inP_reduceplus with (Q := Q); auto.
Qed.

(* Specifications: *)
Theorem red_incl :
forall (a : poly A0 eqA ltM) (p q : list (poly A0 eqA ltM)),
incl p q -> red a p -> red a q.