Haiyan Chen Fengwen Wang Naishuo Tian Jingliang Qian Study on Working Vacation Polling System for WDM with PH Distribution Service Time. 426-429 2008 ISCSCT (1) http://doi.ieeecomputersociety.org/10.1109/ISCSCT.2008.247 conf/iscsct/2008 db/conf/iscsct/iscsct2008-1.html#ChenWTQ08