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. II”. Carpathian Mathematical Publications 12, no. 1 (June 28, 2020): 173-188. Accessed September 18, 2020. https://journals.pnu.edu.ua/index.php/cmp/article/view/3902.