Bakhtin, A. K., and I. V. Denega. “Inequalities for the Inner Radii of Nonorevlapping Domains”. Ukrains’kyi Matematychnyi Zhurnal, vol. 71, no. 7, July 2019, pp. 996-1002, https://umj.imath.kiev.ua/index.php/umj/article/view/1492.