Orumbayeva, N.T., T.D. Tokmagambetova, and Zh.N. Nurgalieva. 2021. “On the Solvability of a Semi-Periodic Boundary Value Problem for the Nonlinear Goursat Equation”. Bulletin of the Karaganda University. Mathematics Series 104 (4):110-17. https://doi.org/10.31489/2021m4/110-117.