1. V. I. Smirnov, Course of Higher Mathematics (Nauka, Moscow, 1967), Vol. 2 [in Russian].
2. A. Kratzer and W. Franz, Transcendental Functions (Akademische Verlaggeselschaft, Leipzig, 1960).
3. A. F. Nikiforov and V. B. Uvarov, Special Functions of Mathematical Physics (Nauka, Moscow, 1984) [in Russian].
4. N. S. Bakhvalov, Numerical Methods (Nauka, Moscow, 1973) [in Russian].
5. R. Varga, Functional Analysis and Approximation Theory in Numerical Analysis (SIAM, Philadelphia, 1971).