diff --git a/Eask b/Eask
index 80d28b2..3d66e36 100644
--- a/Eask
+++ b/Eask
@@ -11,6 +11,7 @@
 (source "melpa")
 
 (depends-on "emacs" "26.1")
+(depends-on "undo-tree")
 (depends-on "fill-page")
 
 (setq network-security-level 'low)  ; see https://github.com/jcs090218/setup-emacs-windows/issues/156#issuecomment-932956432
diff --git a/README.md b/README.md
index d9ce563..1551c75 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,13 @@
 
 [![CI](https://github.com/jcs-elpa/undo-tree-vf/actions/workflows/test.yml/badge.svg)](https://github.com/jcs-elpa/undo-tree-vf/actions/workflows/test.yml)
 
+## 🔨 Usage
+
+```elisp
+(define-key global-map (kbd "C-z") #'undo-tree-vf-undo)
+(define-key global-map (kbd "C-y") #'undo-tree-vf-redo)
+```
+
 ## Contribute
 
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com)
diff --git a/undo-tree-vf.el b/undo-tree-vf.el
index ab671e7..8ed1f5a 100644
--- a/undo-tree-vf.el
+++ b/undo-tree-vf.el
@@ -6,7 +6,7 @@
 ;; Maintainer: Shen, Jen-Chieh <jcs090218@gmail.com>
 ;; URL: https://github.com/jcs-elpa/undo-tree-vf
 ;; Version: 0.1.0
-;; Package-Requires: ((emacs "26.1") (fill-page "0.3.7"))
+;; Package-Requires: ((emacs "26.1") (undo-tree "0.8.2") (fill-page "0.3.7"))
 ;; Keywords: convenience
 
 ;; This file is not part of GNU Emacs.