Remove broken link to astropy docs
astropy.vo has been removed in astropy 3.0. I have added a new
reference to the Simple-Cone-Search-Creator tool.
@@ -14,8 +14,10 @@ Introduction
Astroquery is a set of tools for querying astronomical web forms and databases.
There are two other packages with complimentary functionality as Astroquery:
-`astropy.vo <http://docs.astropy.org/en/latest/vo/index.html>`_ is in the Astropy core and
-`pyvo <https://pyvo.readthedocs.io/en/latest/>`_ is an Astropy affiliated package.
+`pyvo <https://pyvo.readthedocs.io/en/latest/>`_ is an Astropy affiliated package, and
+`Simple-Cone-Search-Creator <https://github.com/tboch/Simple-Cone-Search-Creator/>`_ to
+generate a cone search service complying with the
+`IVOA standard <http://www.ivoa.net/documents/latest/ConeSearch.html>`_.
They are more oriented to general `virtual observatory <http://www.virtualobservatory.org>`_
discovery and queries, whereas Astroquery has web service specific interfaces.
