Peter T. Sander Steven W. Zucker Inferring Surface Trace and Differential Structure from 3-D Images. 833-854 1990 12 IEEE Trans. Pattern Anal. Mach. Intell. 9 http://doi.ieeecomputersociety.org/10.1109/34.57680 db/journals/pami/pami12.html#SanderZ90