proposition: Lemma submx_rowsub (m n p q : nat) (h : 'I_n -> 'I_p) f g (A : 'M_(m, q)) : f =1 g \o h -> (rowsub f A <= rowsub g A)%MS.
proof: Proof. by move=> /eq_rowsub->; rewrite rowsub_comp_sub. 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)