diff --git a/en/src/SUMMARY.md b/en/src/SUMMARY.md
index 17e7cb9..af3163c 100644
--- a/en/src/SUMMARY.md
+++ b/en/src/SUMMARY.md
@@ -2,6 +2,8 @@
 
 [**Introduction**](introduction.md)
 
+[**中文**](../zh/introduction.md)
+
 ---
 
 # Part I: The Vision
diff --git a/zh/src/SUMMARY.md b/zh/src/SUMMARY.md
index c6a3018..90f0cdc 100644
--- a/zh/src/SUMMARY.md
+++ b/zh/src/SUMMARY.md
@@ -2,6 +2,8 @@
 
 [**引言**](introduction.md)
 
+[**English**](../en/introduction.md)
+
 ---
 
 # 第一部分：愿景 (The Vision)