proposition: Lemma normalJ A B x : (A :^ x <| B :^ x) = (A <| B).
proof: Proof. by rewrite /normal normJ !conjSg. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)