.. _`matplotlib`: http://matplotlib.org/
.. _`NumPy`: http://numpy.org/
.. _`SciPy`: http://scipy.org/
.. _`IPython`: http://ipython.org
.. _CIAO: http://cxc.harvard.edu/ciao/
.. _SAS: http://xmm.vilspa.esa.es/sas/
.. _APLpy: http://aplpy.github.com
.. _SAMPy: http://pypi.python.org/pypi/sampy
.. _COATPy: https://github.com/python4vo/coatpy
.. _vaods9: https://github.com/python4vo/vaods9
.. _pyvolib: https://code.google.com/p/pyvolib
.. _ds9: http://hea-www.harvard.edu/RD/ds9
.. _TOPCAT: http://www.star.bris.ac.uk/~mbt/topcat
.. _Directory: http://nvo.stsci.edu/vor10/index.aspx
.. _astropy: http://astropy.org
.. _astropy_doc: http://docs.astropy.org/en/stable
.. _`astropy.io.ascii`: http://docs.astropy.org/en/stable/io/ascii/
.. _`astropy.io.fits`: http://docs.astropy.org/en/stable/io/fits/