fact: Definition lin_mulmx A : 'M[R]_(n * p, m * p) := lin_mx (mulmx A).
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)