proposition: Lemma norms_norm : A \subset 'N('N(B)).
proof: Proof. by apply/normsP=> x Ax; rewrite -normJ (normsP nBA). Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)