proposition: Lemma gcdsr_mulr : forall a p, gcdsr (p * a%:P) %= gcdsr p * a.
proof: Proof. by move=> a p; rewrite mulrC [_ * a]mulrC gcdsr_mull. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(path choice fintype tuple finset ssralg) mathcomp(matrix poly) mathcomp(bigop polydiv) CoqEAL(stronglydiscrete dvdring)