M. Sabry Hassouna Alaa E. Abdel-Hakim Aly A. Farag PDE-based robust robotic navigation. 10-18 2009 27 Image Vision Comput. 1-2 http://dx.doi.org/10.1016/j.imavis.2007.03.005 db/journals/ivc/ivc27.html#HassounaAF09