`{Univalence} : GroupIsomorphism (Pi 1 T) (grp_prod abgroup_Z abgroup_Z). Proof. etransitivity. 1: exact (emap (Pi 1) pequiv_torus_prod_circles). etransitivity. 1: apply grp_iso_pi_prod. apply grp_iso_prod. 1,2: apply pi1_circle. Defined.
Require Import Basics Types. Require Import Pointed WildCat. Require Import Modalities.ReflectiveSubuniverse Truncations.Core. Require Import Algebra.AbGroups. Require Import Homotopy.HomotopyGroup. Require Import Homotopy.PinSn. Require Import Spaces.Int Spaces.Circle. Require Import Spaces.Torus.Torus. Require Import Spaces.Torus.TorusEquivCircles.