proposition: Lemma center_mxP m n A (R : 'A_(m, n)) : reflect (A \in R /\ forall B, B \in R -> B *m A = A *m B) (A \in 'Z(R))%MS.
proof: Proof. rewrite sub_capmx; case R_A: (A \in R); last by right; case. by apply: (iffP cent_mxP) => [cAR | [_ cAR]]. 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 finalg zmodp matrix)