intros Q p; case p; simpl in |- *; auto.
intros H'; elim (inPolySet_is_pX (pO A n) Q);
[ intros a E; elim E; intros q E0; inversion E0 | idtac ];
auto.
intros a l H'.
cut (canonical A0 eqA ltM (pX a l)); [ intros Op0 | idtac ].
cut (canonical A0 eqA ltM l);
[ intros Op1 | apply canonical_imp_canonical with (a := a) ];
auto.
cut (~ zeroP (A:=A) A0 eqA (n:=n) a); [ intros Nza | idtac ].
cut
(spminusf A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec a a Nza l
l = pO A n).
intros H'0; rewrite <- H'0.
change
(reduce Q (pX a l)
(spminusf A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec a a
Nza l l)) in |- *.
apply reducetop with (b := a) (nZb := Nza) (q := l); auto.
apply divP_on_eqT with (1 := cs); auto.
cut
(eqP A eqA n
(spminusf A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec a a
Nza l l) (pO A n)).
intros H'0; inversion H'0; auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec l
(mults (A:=A) multA (n:=n)
(divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) a (b:=a) Nza)
l)); auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec l
(mults (A:=A) multA (n:=n) (T1 A1 n) l));
auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with (y := minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec l l);
auto.
apply minuspf_refl with (1 := cs); auto.
apply (canonical_nzeroP A A0 eqA n ltM) with (p := l); auto.
apply inPolySet_imp_canonical with (L := Q); auto.
Qed.

Theorem ltP_reduce :
forall (Q : list (poly A0 eqA ltM)) (p q : list (Term A n)),
reduce Q p q -> canonical A0 eqA ltM p -> ltP (A:=A) (n:=n) ltM q p.