intros P R H' a b H'0 H'1; simpl in |- *.
apply OBuch_Inv_f with (P := P); auto.
rewrite H'; simpl in |- *; auto.
case (pbuchf (P, genOCPf P)); simpl in |- *; auto.
Qed.
Definition buch : list (poly A0 eqA ltM) -> list (poly A0 eqA ltM).
intros P; exact (strip _ (pbuchf (P, genOCPf P))).
Defined.

Theorem buch_Stable : forall P : list (poly A0 eqA ltM), stable P (buch P).
intros P; apply pbuchf_Stable; auto.