Fact prodv_is_aspace E F : is_aspace (E * F).
Canonical prodv_aspace E F : {subfield L} := ASpace (prodv_is_aspace E F).
Fact field_mem_algid E F : algid E \in F. Proof. by rewrite algid1 mem1v. Qed.
Canonical capv_aspace E F : {subfield L} := aspace_cap (field_mem_algid E F).

Lemma polyOverSv U V : (U <= V)%VS -> {subset polyOver U <= polyOver V}.