PleshakovM. G. and PopovP. A. (2004) “Second Jackson Inequality in a Sign-Preserving Approximation of Periodic Functions”, Ukrains’kyi Matematychnyi Zhurnal, 56(1), pp. 123-128. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3734 (Accessed: 27July2024).