Muratbekov, Musakan, and Mukhtarbai Otelbaev. “On the Existence of a Resolvent and Separability for a Class of Singular Hyperbolic Type Differential Operators on an Unbounded Domain”. Eurasian Mathematical Journal 7, no. 1 (March 30, 2016): 50–67. Accessed October 31, 2025. https://emj.enu.kz/index.php/main/article/view/627.