Keldibekova, A.B. “Solvability of a Semi-Periodic Boundary Value Problem for a Third Order Differential Equation With Mixed Derivative”. Bulletin of the Karaganda University. Mathematics Series 98, no. 2 (June 30, 2020): 84–99. Accessed September 1, 2025. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/363.