Bakhtin, A. K. “Sharp Estimates for Inner Radii of Systems of Nonoverlapping Domains and Open Sets”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 12 (December 25, 2007): 1601–1618. Accessed February 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3416.