proposition: Lemma qisom_isog : [set: coset_of G] \isog [set: coset_of H].
proof: Proof. exact: isom_isog qisom_isom. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)