Kostyshyn, L. P., and B. A. Shuvar. “Aggregate-Iterative Methods for the Approximation of Solutions of Boundary-Value Problems”. Ukrains’kyi Matematychnyi Zhurnal 55, no. 10 (October 25, 2003): 1425-1431. Accessed May 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4011.