[1] J. ?krá?ek and Z. Tichy, “Základy Aplikované Matematiky I, II, III (Basics of Applied Mathematics I, II, III),” SNTL Prague, 1986, p. 2625.
[2] A. Sve?nikov, “Sbírka úloh z Teorie Pravděpodobnosti, Matematické Statistiky a Teorie Náhodnych Funkcií (Set of Tasks from Theory of Probability, Mathematical Statistics and Theory of Random Functions),” SNTL Prague, 1971, p. 640.
[3] J. S. Ventcel, “Teória Pravdepodobnosti (Theory of Probability),” ALFA-SNTL Bratislava-Prague, 1973, p. 522.
[4] G. ?ep?iansky and L. Schwartz, “A Note on Tariffication Strategy Cases in Telecommunications,” NETNOMICS, Springer Science + Business Media LLC, 2009.