Zhipeng Cai Zhi-Zhong Chen Guohui Lin Lusheng Wang An Improved Approximation Algorithm for the Capacitated Multicast Tree Routing Problem. 286-295 2008 COCOA http://dx.doi.org/10.1007/978-3-540-85097-7_27 conf/cocoa/2008 db/conf/cocoa/cocoa2008.html#CaiCLW08