Babenko, V. F., and V. A. Zontov. “Bernstein-Type Inequalities for Splines Defined on the Real Axis”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 63, no. 5, May 2011, pp. 603-11, https://umj.imath.kiev.ua/index.php/umj/article/view/2746.