intros x; generalize wf_Tl; auto.
Qed.
Let Co :=
lexprod (list (poly A0 eqA ltM)) FPset
(RO A A0 A1 eqA plusA invA minusA multA divA cs eqA_dec n ltM ltM_dec os)
Fl.

Theorem wf_Co : well_founded Co.
unfold Co in |- *; apply wf_lexprod.