.. _wcslib: http://www.atnf.csiro.au/~mcalabre/WCS/
.. _distortion paper: http://www.atnf.csiro.au/people/mcalabre/WCS/dcs_20040422.pdf
.. _SIP: http://irsa.ipac.caltech.edu/data/SPITZER/docs/files/spitzer/shupeADASS.pdf
.. _ds9: http://hea-www.harvard.edu/RD/ds9/
