Baranetskij, Ya.O., P.I. Kalenyuk, M.I. Kopach, and A.V. Solomko. “The Nonlocal Boundary Value Problem With Perturbations of Mixed Boundary Conditions for an Elliptic Equation With Constant Coefficients. I”. Carpathian Mathematical Publications 11, no. 2 (December 31, 2019): 228–239. Accessed April 23, 2024. https://scijournals.pnu.edu.ua/index.php/cmp/article/view/2103.