Danny Z. Chen Xiaobo Sharon Hu Shuang Luan Shahid A. Naqvi Chao Wang Cedric X. Yu Generalized Geometric Approaches for Leaf Sequencing Problems in Radiation Therapy. 175-204 2006 16 Int. J. Comput. Geometry Appl. 2-3 http://dx.doi.org/10.1142/S0218195906001999 db/journals/ijcga/ijcga16.html#ChenHLNWY06