Muratbekov, M.B., and Ye.N. Bayandiyev. “Existence and Smoothness of Solutions of a Singular Differential Equation of Hyperbolic Type”. Bulletin of the Karaganda University. Mathematics Series 107, no. 3 (September 30, 2022): 98–104. Accessed July 10, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/524.