LigunA. A., and ShumeikoA. A. “On Lower Bounds for the Approximation of Individual Functions by Local Splines With Nonfixed Nodes”. Ukrains’kyi Matematychnyi Zhurnal 51, no. 12 (December 25, 1999): 1628–1637. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4767.