fact: Variables (m1 m2 n : nat) (A : 'M_(m1, n)) (B : 'M_(m2, n)).
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)