intros Q a b p q H'; generalize a b; clear a b; elim H'; auto.
intros x y z H'0 H'1 H'2 a b H'3 H'4.
apply Rstar_n with (y := pX b y); auto.
apply H'2; auto.
apply ltP_pX_canonical; auto.
apply canonical_reduce with (1 := cs) (3 := H'0); auto.
apply canonical_imp_canonical with (a := a); auto.
apply canonical_nzeroP with (ltM := ltM) (p := x); auto.
apply eqp_imp_canonical with (1 := cs) (p := pX a x); auto.
apply ltP_trans with (y := x); auto.
apply ltP_reduce with (1 := cs) (3 := H'0); auto.
apply canonical_imp_canonical with (a := a); auto.
apply (canonical_pX_ltP A A0 eqA); auto.
apply eqp_imp_canonical with (1 := cs) (p := pX a x); auto.
Qed.
Hint Resolve reduceplus_skip.

Theorem reduce_imp_reduceplus :
forall (Q : list (poly A0 eqA ltM)) (p q : list (Term A n)),
reduce A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q p q ->
reduceplus Q p q.