Prymak, A. V. “Shape-Preserving Smoothing of 3-Convex Splines of Degree 4”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 2 (February 25, 2005): 277–283. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3596.