[1] Feller, W: An introduction to probability theory and its applications. New York 1950. Zbl 0039.13201

[2] Chung K. L.: Markov chains with stationary transition probabilities. Berlin 1960. MR 0116388 | Zbl 0092.34304

[3] Karlin S., McGregor J.: The differential equations of birth - and - death processes and the Stieltjes moment problem. Trans. of Amer. Math. Soc. 85 (1957), 489-546. MR 0091566 | Zbl 0091.13801