proposition: Lemma im_qisom_proof : 'N(H) \subset 'N(G).
proof: Proof. by rewrite eqGH. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)