proposition: Lemma xrowEsub i1 i2 : xrow i1 i2 = rowsub (tperm i1 i2).
proof: Proof. exact: 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)