M. L. Gorbachuk and R. Y. Yakymiv, “Estimate of error of an approximated solution by the method of moments of an operator equation”, Ukr. Mat. Zhurn., vol. 48, no. 11, pp. 1477–1483, Nov. 1996, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5201