proposition: Lemma xcolEsub j1 j2 : xcol j1 j2 = colsub (tperm j1 j2).
proof: Proof. exact: col_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)