We cite [REL09]_ or REL09_
or even rel09_. See REL08_.

.. [REL09] Citation

.. <warning descr="Duplicate explicit target name 'REL08'">[REL08]</warning> Citation
.. <warning descr="Duplicate explicit target name 'REL08'">[REL08]</warning> Citation2

.. <warning descr="Duplicate explicit target name 'new link'">_`new link`:</warning> http://python.org
.. <warning descr="Duplicate explicit target name 'new link'">_new link:</warning> http://pythonic.org