Variables F : fieldType.
Local Notation "A \in R" := (@submx F _ _ _ (mxvec A) R).

(* Specifications: *)
Lemma mem0mx m n (R : 'A_(m, n)) : 0 \in R.
Lemma memmx_subP m1 m2 n (R1 : 'A_(m1, n)) (R2 : 'A_(m2, n)) :
reflect (forall A, A \in R1 -> A \in R2) (R1 <= R2)%MS.