1. S. L. Sobolev, Partial Differential Equations of Mathematical Physics (Gos. Izd-vo Tekh.-Teor. Lit., Moscow, 1954; Pergamon Press, Oxford, 1964). https://doi.org/10.1016/B978-0-08-010424-9.50002-0
2. V. S. Vladimirov, Equations of Mathematical Physics (Nauka, Moscow, 1971; Marcel Dekker, New York, 1971).
3. I. G. Petrovsky, Lectures on Partial Differential Equations (GIFML, Moscow, 1961; Dover, New York, 2012).
4. L. A. Lyusternik and V. I. Sobolev, Elements of Functional Analysis (GIFML, Moscow, 1965).
5. A. N. Tikhonov and A. A. Samarskii, Equations of Mathematical Physics (Nauka, Moscow, 1977; Dover, New York, 2013).