proposition: Lemma maxnormal_proper A B C : maxnormal A B C -> A \proper B.
proof: Proof. by case/maxsetP=> /and3P[gA pAB _] _; apply: (sub_proper_trans (subset_gen A)). Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(fintype bigop finset fingroup morphism) mathcomp(automorphism quotient action commutator center)