.. _matplotlib: https://matplotlib.org
.. _Numpy: https://www.numpy.org
.. _Healpy: https://healpy.readthedocs.io
.. _scikit-image: http://scikit-image.org
.. _Pillow: https://python-pillow.org/
.. _HiPS paper: https://www.aanda.org/articles/aa/pdf/2015/06/aa26075-15.pdf
.. _HiPS IVOA recommendation: http://www.ivoa.net/documents/HiPS/
.. _HiPS at CDS: http://aladin.u-strasbg.fr/hips/