Svetlana Barsky Maria Petrou The 4-Source Photometric Stereo Technique for Three-Dimensional Surfaces in the Presence of Highlights and Shadows. 1239-1252 2003 25 IEEE Trans. Pattern Anal. Mach. Intell. 10 http://doi.ieeecomputersociety.org/10.1109/TPAMI.2003.1233898 db/journals/pami/pami25.html#BarskyP03