William D. Toczyski Nikolaos Papanikolopoulos Complementary Linear Biases in Spatial Derivative Estimation for Improving Geometry-Driven Diffusion Processes. 3001-3006 2000 ICPR db/conf/icpr/icpr2000-3.html#ToczyskiP00 http://csdl.computer.org/comp/proceedings/icpr/2000/0750/03/07503001abs.htm