1. Ayyappan Govindan Muthu Ganapathy Subramanian and Gopal Sekar, Single Server Retrial Queueing System with Variable Service Rates in Priority Service by matrix geometric method, International Journal of Applied mathematics & Computation, vol. 3, pp. 216–231, 2011
2. The M/G/1 queue with disasters and working breakdowns
3. The M/M/c retrial queue with geometric loss and feedback
4. Choi, B. D., Kulkarni, V. G., Feedback retrial queueing system, Stochastic Model Relat. Fields, pp. 93–105, (1992).