Jiguo Yu Suxia Cui Guanghui Wang An Algorithm with Better Approximation Ratio for Multicast Traffic in Unidirectional SONET/WDM Rings. 530-540 2009 COCOA http://dx.doi.org/10.1007/978-3-642-02026-1_50 conf/cocoa/2009 db/conf/cocoa/cocoa2009.html#YuCW09a