1. N. I. Muskhelishvili, Singular Integral Equations (Nauka, Moscow, 1968; Wolters-Noordhoff, Groningen, 1972).
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3. F. D. Gakhov, Boundary Value Problems (Nauka, Moscow, 1977; Dover, New York, 1990).
4. A. P. Soldatov, Douglis Analytic Functions (Novgorod. Gos. Univ., Novgorod, 1995) [in Russian].
5. A. P. Soldatov, “Hyperanalytic functions and their applications,” J. Math. Sci. 132, 827–882 (2006).