1. U. Grenander, “Stochastic groups,” Arkiv. Mat.,4, 189–207 (1961).
2. G. Lev, “Semi-Markov birth and death processes,” Teoriya Veroyatn. i Ee Primen.,17, No. 1, 160–166 (1972).
3. G. Lev, “Asymptotic properties of probability of degeneration for semi-Markov birth processes,” Teoriya Veroyatn. i Ee Primen.,18, No. 4, 778–789 (1973).
4. W. Feller, Introduction to Probability Theory and Its Applications, Vol. 2, Wiley (1968).
5. V. Maksimov, “Generalized Bernoulli scheme and its limit distribution,” Teoriya Veroyatn. i Ee Primen.,18, No. 3, 547–556 (1973).