diff --git a/COPYING b/COPYING
index 48e5a96de7..428ce03ed7 100644
--- a/COPYING
+++ b/COPYING
@@ -1,3 +1,5 @@
+{日本語}[rdoc-ref:COPYING.ja]
+
 Ruby is copyrighted free software by Yukihiro Matsumoto <matz@netlab.jp>.
 You can redistribute it and/or modify it under either the terms of the
 2-clause BSDL (see the file BSDL), or the conditions below:
diff --git a/COPYING.ja b/COPYING.ja
index 230376bc60..5de2dbcc8f 100644
--- a/COPYING.ja
+++ b/COPYING.ja
@@ -1,3 +1,5 @@
+{English}[rdoc-ref:COPYING]
+
 本プログラムはフリーソフトウェアです．2-clause BSDL
 または以下に示す条件で本プログラムを再配布できます
 2-clause BSDLについてはBSDLファイルを参照して下さい．
diff --git a/doc/extension.ja.rdoc b/doc/extension.ja.rdoc
index 2f7856f3d4..381b94a230 100644
--- a/doc/extension.ja.rdoc
+++ b/doc/extension.ja.rdoc
@@ -1,5 +1,7 @@
 # extension.ja.rdoc -  -*- RDoc -*- created at: Mon Aug  7 16:45:54 JST 1995
 
+{English}[rdoc-ref:extension.rdoc]
+
 = Rubyの拡張ライブラリの作り方
 
 Rubyの拡張ライブラリの作り方を説明します．
diff --git a/doc/extension.rdoc b/doc/extension.rdoc
index 6cf4c4926c..18dc5817d4 100644
--- a/doc/extension.rdoc
+++ b/doc/extension.rdoc
@@ -1,5 +1,7 @@
 # extension.rdoc -  -*- RDoc -*- created at: Mon Aug  7 16:45:54 JST 1995
 
+{日本語}[rdoc-ref:extension.ja.rdoc]
+
 = Creating extension libraries for Ruby
 
 This document explains how to make extension libraries for Ruby.