proposition: Lemma center_abelian G : abelian 'Z(G).
proof: Proof. by rewrite /abelian subIset // centsC subIset // subxx orbT. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient action gproduct gfunctor) mathcomp(cyclic)