1. I. E. Pleshchinskaya and N. B. Pleshchinskii, ‘‘Over-determined boundary value problems for elliptical partial differential equations and their application to theory of wave diffraction,’’ Uch. Zap. Kazan. Univ. 147 (3), 4–32 (2005).
2. I. E. Pleshchinskaya and N. B. Pleshchinskii, ‘‘On mixed boundary value problems for set of partial differential equations with constant coefficients in semi-spaces,’’ Lobachevskii J. Math. 39, 1090–1098 (2018).
3. A. N. Tikhonov and A. A. Samarskii, Equations of Mathematical Physics (Nauka, Moscow, 1972; Pergamon, Oxford, 1964).
4. G. N. Polozhii, Equations of Mathematical Physics (Vysshaya Shkola, Moscow, 1964) [in Russian].
5. M. A. Lavrent’ev and B. V. Shabat, Methods of Theory of Functions of Complex Variables (Nauka, Moscow, 1987) [in Russian].