proposition: Lemma morphim_qisom A : qisom @* (A / G) = A / H.
proof: Proof. by rewrite morphim_restrm setTI morphim_factm. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)