proposition: Lemma norm_acts_max_norm P : [acts 'N(P), on |/|*(P; pi) | 'JG].
proof: Proof. apply/subsetP=> z Nz; rewrite !inE; apply/subsetP=> Q; rewrite !inE. case/maxgroupP=> qQ maxQ; apply/maxgroupP; rewrite pgroupJ norm_conj_norm //. split=> // Y; rewrite sub_conjg /= => qY; move/maxQ=> <-; rewrite ?conjsgKV //. by rewrite pgroupJ norm_conj_norm ?groupV. Qed.
imports: HB(structures) mathcomp.ssreflect.ssreflect mathcomp(ssrbool ssrfun eqtype ssrnat seq div choice fintype bigop) mathcomp(finset prime fingroup morphism automorphism action quotient) mathcomp(gfunctor cyclic pgroup center commutator gseries nilpotent) mathcomp(sylow abelian maximal hall) odd_order(BGsection1 BGsection6)