Berdyshev, Abdumauvlen, Anvar Hasanov, and Ainur Ryskan. “Solution of the Neumann Problem for One Four-Dimensional Elliptic Equation”. Eurasian Mathematical Journal 11, no. 2 (June 30, 2020): 93–97. Accessed September 30, 2026. https://emj.enu.kz/index.php/main/article/view/183.