proposition: Lemma normsD1 A B : A \subset 'N(B) -> A \subset 'N(B^#).
proof: Proof. by move/normsD->; rewrite ?norms1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)