1. A. V. Bitsadze and M. S. Salakhitdinov, ‘‘On the theory of equations of mixed-composite type,’’ Sib. Mat. Zh. 2 (1), 7–19 (1961).
2. M. S. Salahitdinov, Equation of Mixed-Composite Type (Fan, Tashkent, 1974) [in Russian].
3. T. D. Djuraev, Boundary Value Problems for Equations of Mixed and Mixed Composite Types (Fan, Tashkent, 1979) [in Russian].
4. T. D. Djuraev, A. Sopuev, and M. Mamazhonov, Boundary Value Problems for Equations of Parabolic-Hyperbolic Type (Fan, Tashkent, 1986) [in Russian].
5. O. M. Dzhokhadze, ‘‘Influence of lower terms on the correctness of the formulation of characteristic problems for third-order hyperbolic equations,’’ Math. Notes 74, 491–501 (2003).