diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
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+Please see [official issue tracker] and wiki [HowToContribute].
+
+[official issue tracker]: https://bugs.ruby-lang.org
+[HowToContribute]: https://bugs.ruby-lang.org/projects/ruby/wiki/HowToContribute
diff --git a/ChangeLog b/ChangeLog
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+++ b/ChangeLog
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+Mon Jun  2 12:26:08 2014  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
+
+	* CONTRIBUTING.md: added contibuting guide for github. [fix GH-625]
+
 Mon Jun  2 07:30:33 2014  Tanaka Akira  <akr@fsij.org>
 
 	* test/ruby/envutil.rb (default_warning): New method.