RadzievskayaE. I., and RadzievskiiG. V. “On One Extremal Problem for Numerical Series”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 10 (October 25, 2005): 1430–1434. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3698.