proposition: Lemma mem_uniq_mmax U M : 'M(U) = [set M] -> M \in 'M /\ U \subset M.
proof: Proof. by move/setP/(_ M); rewrite set11 => /setIdP. 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)