intros P Q H'; try assumption.
apply OBuch_Stable with (Q := genOCPf P); auto.
intros a H'0; try assumption.
apply genOCPf_stable; auto.
Qed.

Theorem OBuch_Inv_f :
forall P Q : list (poly A0 eqA ltM),
OBuch P (genOCPf P) Q ->
forall a b : poly A0 eqA ltM, In a Q -> In b Q -> reds a b Q.