Polyakov, O. V., and N. O. Polyakova. “Best Cubature Formulas for Some Classes of Continuous Functions of Two Variables”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 4 (April 25, 2009): 572-576. Accessed January 31, 2023. https://umj.imath.kiev.ua/index.php/umj/article/view/3042.