1. A. N. Tikhonov and A. A. Samarskii, Equations of Mathematical Physics (Gostekhteorizdat, Moscow, 1953; Pergamon Press, Oxford, 1964).
2. V. S. Vladimirov, Equations of Mathematical Physics (Marcel Dekker, New York, 1971; Nauka, Moscow, 1976).
3. A. Sveshnikov, A. N. Bogolyubov, and V. V. Kravtsov, Lectures on Mathematical Physics (Nauka, Moscow, 2004) [in Russian].
4. K. I. Babenko, Fundamentals of Numerical Analysis (Nauka, Moscow, 1986) [in Russian].
5. N. S. Bakhvalov, Numerical Methods: Analysis, Algebra, Ordinary Differential Equations (Nauka, Moscow, 1973; Mir, Moscow, 1977).