RontoM. I., SamoilenkoA. M., and TrofimchukS. I. 1999. “The Theory of the Numerical-Analytic Method: Achievements and New Trends of Development. VII”. Ukrains’kyi Matematychnyi Zhurnal 51 (9), 1244–1261. https://umj.imath.kiev.ua/index.php/umj/article/view/4720.