Elets, L. V., and P. A. Masharov. “On One Extremal Problem of Pompeiu Sets”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 1 (January 25, 2009): 61-72. Accessed April 26, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3001.