diff --git a/SUMMARY.md b/SUMMARY.md
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@@ -1,5 +1,6 @@
 # 机器学习
 
+* [致读者](intro.md)
 * [简介](README.md)
 * [第1章：机器学习概述](machine_learning.md)
     * [1.1 什么是机器学习](what's machine_learning.md)