Ariel Tankus Nir A. Sochen Yehezkel Yeshurun Shape-from-Shading Under Perspective Projection. 21-43 2005 63 International Journal of Computer Vision 1 http://dx.doi.org/10.1007/s11263-005-4945-6 db/journals/ijcv/ijcv63.html#TankusSY05