1. E. C. Titchmarsh, Introduction to the Theory of Fourier Integrals (Clarendon, Oxford, 1948; Komkniga, Moscow, 2005).
2. A. N. Tikhonov and A. A. Samarskii, Equations of Mathematical Physics (Pergamon Press, Oxford, 1964; Gostekhteorizdat, Moscow, 1972).
3. V. S. Vladimirov, Equations of Mathematical Physics (Marcel Dekker, New York, 1971; Nauka, Moscow, 1976).
4. A. G. Sveshnikov, A. N. Bogolyubov, and V. V. Kravtsov, Lectures on Mathematical Physics (Nauka, Moscow, 2004) [in Russian].
5. G. N. Watson, Treatise on the Theory of Bessel Functions (Inostrannaya Literatura, Moscow, 1949; Cambridge Univ. Press, Cambridge, 1952).