(A : D) (p : morphism C X (U A)) (Ap := CommaCategory.
Require Import Category.Core Functor.Core. Require Import Category.Dual Functor.Dual. Require Import Category.Objects. Require Import InitialTerminalCategory.Core InitialTerminalCategory.Functors. Import Comma.Core. Require Import Trunc Types.Sigma HoTT.Tactics. Require Import Basics.Tactics.