Gilles Aubert Michel Barlaud Olivier D. Faugeras Stéphanie Jehan-Besson Image Segmentation Using Active Contours: Calculus of Variations or Shape Gradients? 2128-2154 2003 63 SIAM Journal of Applied Mathematics 6 http://dx.doi.org/10.1137/S0036139902408928 db/journals/siamam/siamam63.html#AubertBFJ03