2 citations to https://www.mathnet.ru/rus/tvp1182

1. Marvin K. Nakayama, Perwez Shahabuddin, Karl Sigman, “On finite exponential moments for branching processes and busy periods for queues”, Journal of Applied Probability, 41:A (2004), 273  
2. Marvin K. Nakayama, Perwez Shahabuddin, Karl Sigman, “On finite exponential moments for branching processes and busy periods for queues”, J. Appl. Probab., 41:A (2004), 273