Eleev, V. A., and S. K. Kumykova. “On Some Boundary-Value Problems With a Shift on Characteristics for a Mixed Equation of Hyperbolic-Parabolic Type”. Ukrains’kyi Matematychnyi Zhurnal 52, no. 5 (May 25, 2000): 707–716. Accessed April 7, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/4464.