Musielak, M. “Covering a Reduced Spherical Body by a Disk”. Ukrains’kyi Matematychnyi Zhurnal 72, no. 10 (October 25, 2020): 1400 - 1409. Accessed September 27, 2022. http://umj.imath.kiev.ua/index.php/umj/article/view/6029.