proposition: Lemma perm_mxEsub n s : @perm_mx n s = rowsub s 1%:M.
proof: Proof. by rewrite /perm_mx row_permEsub. 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 countalg finalg zmodp)