MelnikYu. I. “Direct Theorems of Approximation for the Functions Regular in Convex Polygon by Exponential Polynomials in the Integral Metrics ”. Ukrains’kyi Matematychnyi Zhurnal 40, no. 5 (August 29, 1988): 584-591. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/8806.