Babenko, V. F., and N. V. Parfinovych. “Inequalities of the Bernstein Type for Splines of Defect 2”.
Ukrains’kyi Matematychnyi Zhurnal
, vol. 61, no. 7, July 2009, pp. 995-9,
https://umj.imath.kiev.ua/index.php/umj/article/view/3074
.