proposition: Lemma quotient_injG : {in [pred G : {group gT} | H <| G] &, injective (fun G => G / H)}.
proof: Proof. by rewrite /normal -{1}ker_coset; apply: morphim_injG. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)