proposition: Lemma centsC A B : (A \subset 'C(B)) = (B \subset 'C(A)).
proof: Proof. by apply/centsP/centsP=> cAB x ? y ?; rewrite /commute -cAB. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)