1. K. I. Babenko, Foundations of Numerical Analysis [in Russian], Nauka, Moscow (1986).
2. V. L. Goncharov, Theory of Interpolation and Approximation of Functions [in Russian], Gostekhizdat, Moscow, Leningrad (1954).
3. L. Schwartz, Analyse mathematique. I, Hermann, Paris (1967).
4. A. A. Samarskii, R. D. Lazarov, and V. L. Makarov, Difference Schemes for Differential Equations with Generalized Solutions [in Russian], Vyssh. Shkola, Moscow (1987).