diff --git a/algebra/quotient_group.hlean b/algebra/quotient_group.hlean
index c2e0b2b..963cd70 100644
--- a/algebra/quotient_group.hlean
+++ b/algebra/quotient_group.hlean
@@ -247,6 +247,7 @@ namespace group
 
 ------------------------------------------------
   -- FIRST ISOMORPHISM THEOREM
+------------------------------------------------
 
 
 definition kernel_quotient_extension {A B : AbGroup} (f : A →g B) : quotient_ab_group (kernel_subgroup f) →g B :=
@@ -371,7 +372,8 @@ definition is_embedding_kernel_quotient_to_image {A B : AbGroup} (f : A →g B)
     exact is_embedding_kernel_quotient_extension f
   end
 
-definition ab_group_first_iso_thm (A B : AbGroup) (f : A →g B) : quotient_ab_group (kernel_subgroup f) ≃g ab_image f :=
+definition ab_group_first_iso_thm (A B : AbGroup) (f : A →g B) 
+           : quotient_ab_group (kernel_subgroup f) ≃g ab_image f :=
   begin
     fapply isomorphism.mk,
     exact ab_group_kernel_quotient_to_image f,