Make default citation pattern more general

Author: sergiocallegari

numpydoc/numpydoc.py

@@ -134,7 +134,7 @@ def setup(app, get_doc_object_=get_doc_object):
     app.add_config_value('numpydoc_show_class_members', True, True)
     app.add_config_value('numpydoc_show_inherited_class_members', True, True)
     app.add_config_value('numpydoc_class_members_toctree', True, True)
-    app.add_config_value('numpydoc_citation_re', '[a-z0-9_.-]', True)
+    app.add_config_value('numpydoc_citation_re', '[a-z0-9_.-]+', True)
 
     # Extra mangling domains
     app.add_domain(NumpyPythonDomain)