1. N. I. Muskhelishvili, Boundary-Value Problems in the Theory of Functions and Some Applications of Them to Mathematical Physics (Nauka, Moscow, 1968) [in Russian].
2. F. A. Gakhov, Boundary-Value Problems (GIFML, Moscow, 1963) [in Russian].
3. I. N. Vekua, “Systems of differential equations of the first order of elliptic type and boundary value problems, with an application to the theory of shells,” Mat. Sb. 31 (73) (2), 217–314 (1952).
4. G. S. Litvinchuk, Boundary-Value Problems and Singular Integral Equations with Shift (Nauka, Moscow, 1977) [in Russian].
5. I. I. Danilyuk, Nonregular Boundary-Value Problems in the Plane (Nauka, Moscow, 1975) [in Russian].