This software was produced by the United States Naval Observatory at the
expense of United States taxpayers, and is therefore not suseptible to
copyright, because a copyright would place taxpayer property under
private ownership. Since it is not copyrighted, it cannot be licensed;
it is simply free.

To credit the authors, you are invited to cite their work as follows:

**Barron, E. G., Kaplan, G. H., Bangert, J., Bartlett, J. L., Puatua, W., Harris, W., & Barrett, P. (2011)** `"Naval Observatory Vector Astrometry Software (NOVAS) Version 3.1, Introducing a Python Edition," <http://aa.usno.navy.mil/software/novas/novas_py/novas.pdf>`_ **Bull. AAS, 43, 2011.**

The authors of NOVAS ask that if you use their software in your work,
that you let them know at help@aa.usno.navy.mil since a record of who is
using their software helps them justify the excellent work that they are
doing by making the software available to the public.
