intros p L; unfold nf, LetP in |- *; auto.
case
(Reducef A A0 A1 eqA plusA invA minusA multA divA cs eqA_dec n ltM ltM_dec
os L p); simpl in |- *; auto.
intros x0; case x0; simpl in |- *.
intros x c H'.
change
(CombLinear A A0 eqA plusA multA eqA_dec n ltM ltM_dec
(p :: L)
(mults (A:=A) multA (n:=n)
(unit A A0 A1 eqA divA n ltM (mks A A0 eqA n ltM x c)) x))
in |- *.
apply CombLinear_mults1 with (1 := cs); auto.
apply unit_nZ with (1 := cs); auto.
apply reducestar_cb1 with (1 := cs); auto.
Qed.

Theorem Cb_comp :
forall L1 L2 : list (poly A0 eqA ltM),
(forall p : poly A0 eqA ltM,
In p L1 -> Cb A A0 eqA plusA multA eqA_dec n ltM ltM_dec p L2) ->
forall q : poly A0 eqA ltM,
Cb A A0 eqA plusA multA eqA_dec n ltM ltM_dec q L1 ->
Cb A A0 eqA plusA multA eqA_dec n ltM ltM_dec q L2.