proposition: Lemma submxK : block_mx ulsubmx ursubmx dlsubmx drsubmx = A.
proof: Proof. by rewrite /block_mx !hsubmxK vsubmxK. 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)