Seok Ho Chang Tetsuya Takine Factorization and Stochastic Decomposition Properties in Bulk Queues with Generalized Vacations. 165-183 2005 50 Queueing Syst. 2-3 http://dx.doi.org/10.1007/s11134-005-0510-9 db/journals/questa/questa50.html#ChangT05