1. S. Tsoi, “An algorithm for finding the number of paths from a minorant to a majorant in a connected linear complex,” in: Cybernetics in Mining [in Russian], Nauka, Moscow (1966).
2. B. V. Gnedenko et al., Mathematical Methods in the Theory of Reliability [in Russian], Nauka, Moscow (1965).
3. J. Sandler, system Reliability Engineering, Prentice-Hall (1963).
4. R. Howard, Dynamic Programming and Markov Processes [Russian translation], Sovet-skoe Radio (1964).