Irgashev, B. Yu. “Mixed Problem for Higher-Order Equations With Fractional Derivative and Degeneration in Both Variables”. Ukrains’kyi Matematychnyi Zhurnal 74, no. 10 (November 27, 2022): 1328 -1338. Accessed May 10, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/6298.