{A B B' : AbGroup} {f : B' $-> B} {X : AbSES B' A} (E F : graph_hfiber (abses_pullback f) X) := {p : E.
Require Import Basics Types. Require Import HSet Limits.Pullback. Require Import WildCat Pointed.Core Homotopy.ExactSequence. Require Import Modalities.ReflectiveSubuniverse. Require Import AbGroups.AbelianGroup AbGroups.AbPullback AbGroups.Biproduct. Require Import AbSES.Core AbSES.DirectSum.