proposition: Lemma mem0mx m n (R : 'A_(m, n)) : 0 \in R.
proof: Proof. by rewrite linear0 sub0mx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)