doc update: fix links
diff --git a/documentation/index.rst b/documentation/index.rst
index 5ed0ba1..a5eb155 100644
--- a/documentation/index.rst
+++ b/documentation/index.rst
@@ -16,6 +16,7 @@
 - This page, when viewed online is at https://pyserial.readthedocs.org/en/latest/ or
   http://pythonhosted.org/pyserial/ .
 
+.. _Python: http://python.org/
 .. _`project page on GitHub`: https://github.com/pyserial/
 .. _`Download Page`: http://pypi.python.org/pypi/pyserial