proposition: Lemma quotient_abelian A : abelian A -> abelian (A / H).
proof: Proof. exact: morphim_abelian. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)