proposition: Lemma injm_pHall pi G H : G \subset D -> H \subset D -> pi.-Hall(f @* G) (f @* H) = pi.-Hall(G) H.
proof: Proof. by move=> sGD sGH; rewrite !pHallE injmSK ?card_injm. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)