Copyright (C) 1997, 2000 University of Texas Board of Regents*

The Hilbert encoding algorithm was written by H. Carter Edwards in
1997 while a graduate student at the University of Texas at Austin.
This portion of the sfcurves library is licensed under the GNU GPLv1.

The Morton encoding algorithm was written by William L. Barth around
2000 while a graduate student at the University of Texas at Austin.
This portion of the sfcurves library is licensed under the GNU GPLv2.

* Both authors were employed as graduate students at the University of
  Texas at the time they authored this work, therefore the work-for-hire
  (http://copyright.lib.utexas.edu/whoowns.html) rules apply.