Motornaya, O. V., and V. P. Motornyi. “On the Joint Approximation of a Function and Its Derivatives in the Mean”. Ukrains’kyi Matematychnyi Zhurnal 71, no. 2 (February 25, 2019): 261–270. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1436.