[1]
H. A. Dzyubenko, “Comonotone approximation of twice differentiable periodic functions”, Ukr. Mat. Zhurn., vol. 61, no. 4, pp. 435–451, Apr. 2009, Accessed: Dec. 07, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3032