fact: Definition Sylvester_mx : 'M[R]_dS := col_mx (band p) (band q).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(div fintype tuple finfun bigop fingroup perm) mathcomp(ssralg zmodp matrix mxalgebra poly polydiv)