BabenkoV. F., & LeisA. (1998). The best $L_1$-approximations of classes of functions defined by differential operators in terms of generalized splines from these classes. Ukrains’kyi Matematychnyi Zhurnal, 50(11), 1443-1451. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4796