Imanbaev, N.S., and M.N. Ospanov. “On Eigenvalues of Third Order Composite Type Equations With Regular Boundary Value Conditions”. Bulletin of the Karaganda University. Mathematics Series 96, no. 4 (December 30, 2019): 44–51. Accessed December 8, 2025. https://mts.buketov.edu.kz/mathematics-vestnik/article/view/332.