1. Poryazov, S. A. “User and Terminal Teletraffic — Classification and Notations”. Conference Telecom’2000, Varna, Bulgaria (in print).
2. Poryazov, S. A. “Determining the Basic Traffic and Time Characteristics of Telephone Systems with Nonhomogeneous Subscribers”. MCTTKM-4, Moscow, Russia, 20–25 October 1992, pp. 130–138.
3. Poryazov, S. A. “Parameters For Subscribers’ Traffic Measurement with Nonhomogeneous Subscribers”. Conference Telecom’2000, Varna, Bulgaria (in print).