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