kungifu is described in an invited contribution to a special
gravitational lensing issue of the New Journal of Physics,
which is freely accessible online via the following url:
http://www.iop.org/EJ/abstract/1367-2630/9/12/443/
ANY PUBLICATION RESULTING FROM THE USE OF kungifu MUST INCLUDE
A CITATION TO THIS ARTICLE.
\bibitem[Bolton \& Burles(2007)]{2007NJPh....9..443B}
Bolton, A.~S., \& Burles, S.\ 2007, New Journal of Physics, 9, 443