proposition: Lemma maxainv_norm : maxainv K N -> N <| K.
proof: Proof. by move/maxgroupp; case/andP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(automorphism quotient action gseries)