worth giving PyPy a try. On a suite of benchmarks, it's current `over 5 times
faster than CPython <http://speed.pypy.org/>`_.
-Currently PyPy supports Python 2.7.
+Currently PyPy supports Python 2.7. [#pypy_ver]_
Jython
------
If you need to interface with an existing Java codebase or have other reasons to
need to write Python code for the JVM, Jython is the best choice.
-Currently Jython supports up to Python 2.5.
+Currently Jython supports up to Python 2.5. [#jython_ver]_
IronPython
----------
IronPython directly in to the Visual Studio development environment, making it
an ideal choice for Windows developers.
-IronPython supports Python 2.7.
+IronPython supports Python 2.7. [#iron_ver]_
+
+.. [#pypy_ver] http://pypy.org/compat.html
+
+.. [#jython_ver] http://wiki.python.org/jython/JythonFaq/GeneralInfo#Is_Jython_the_same_language_as_Python.3F
+
+.. [#iron_ver] http://ironpython.codeplex.com/releases/view/54498
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