diff --git a/.document b/.document
new file mode 100644
index 0000000..f7b50c8
--- /dev/null
+++ b/.document
@@ -0,0 +1,6 @@
+COPYING
+ChangeLog
+README.md
+_doc/
+ext/
+logs/ChangeLog-*
diff --git a/.rdoc_options b/.rdoc_options
new file mode 100644
index 0000000..f9297d9
--- /dev/null
+++ b/.rdoc_options
@@ -0,0 +1,2 @@
+---
+main_page: README.md
diff --git a/_doc/io.rb b/_doc/io.rb
new file mode 100644
index 0000000..da9f79e
--- /dev/null
+++ b/_doc/io.rb
@@ -0,0 +1,3 @@
+# See {IO}[https://docs.ruby-lang.org/en/master/IO.html]
+class IO
+end