Клюс, І.С. “Multipoint Problem for Intehrodyferentsialnyh Partial Differential Equations, Not Solvable on Higher Derivatives”. Proceedings of National Aviation University 31, no. 1 (January 1, 2007): 189–191. Accessed May 6, 2024. https://jrnl.nau.edu.ua/index.php/visnik/article/view/1459.