BabenkoV. F., and ParfinovychN. V. “Nonsymmetric Approximations of Classes of Periodic Functions by Splines of Defect 2 and Jackson-Type Inequalities”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 11 (November 25, 2009): 1443-1454. Accessed November 23, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3113.