Mads Nielsen Luc Florack Rachid Deriche Regularization, Scale-Space, and Edge Detection Filters. 70-81 1996 conf/eccv/1996-2 ECCV (2) db/conf/eccv/eccv1996-2.html#NielsenFD96 http://dx.doi.org/10.1007/3-540-61123-1_128