Notation "A / H" := (quotient A H) : group_scope.Implicit Types A : {set gT}.Implicit Types (C D : {set coset_of H}) (L M : {group coset_of H}).Notation "A / H" := (quotient_group A H) : Group_scope.

Lemma quotient_abelian A : abelian A -> abelian (A / H).