proposition: Lemma mor_of_mx_proof : pres M %| pres source_of_mx *m X.
proof: Proof. by rewrite -dvd_ker. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements stronglydiscrete coherent edr