intros L1; elim L1; simpl in |- *; auto.
intros L2 p H'; elim H'; auto.
unfold LetP in |- *.
intros a l H' L2 p H'0; case H'0;
[ intros H'1; rewrite H'1; clear H'0 | intros H'1; clear H'0 ];
auto.
case (zerop_dec (nf (l ++ L2) p)); auto.
intros H'0.
apply cb_comp with (L1 := l ++ L2); auto.
intros p0 H'2.
lapply (in_app_or l L2 p0); auto.
intros H'3; case H'3; auto.
intros H'0.
2: case (zerop_dec (nf (l ++ L2) a)); auto.
2: intros H'0.
2: apply
cb_incl
with (L1 := redacc l (nf (l ++ L2) a :: L2) ++ nf (l ++ L2) a :: L2);
auto with datatypes.
apply cb_compo with (L1 := nf (l ++ L2) p :: l ++ L2); simpl in |- *; auto.
intros q H'2; case H'2;
[ intros H'3; rewrite <- H'3; clear H'2 | intros H'3; clear H'2 ];
auto with datatypes.
case (in_app_or l L2 q H'3); auto with datatypes.
intros H'2.
apply
cb_incl with (L1 := redacc l (nf (l ++ L2) p :: L2) ++ nf (l ++ L2) p :: L2);
auto with datatypes.
Qed.

Theorem cb_red : forall (L : list poly) (p : poly), In p L -> cb (red L) p.
intros L p H'.