Application of the method of collective marks to some M/G/1 vacation models with exhaustive service / by Tang Doc CongA Takacs-type equation in the m/g/1 queue with N-policy and setup times / by Tang Doc CongTime-dependent distribution of the workload in M/G/1 vacation models : a unified approach / T.C. [i.e. T.D.] CongVirtual waiting time and depletion time in m/g/1 queues with vacations / by Tang Dac CongCollective marks and waiting-time problems / Tang Dac Cong