proposition: Lemma repr_coset_norm xbar : repr xbar \in 'N(H).
proof: Proof. exact: subsetP (coset_norm _) _ (mem_repr_coset _). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)