Bakhtin, A. K., and V. E. V’yun. “Application of a Separating Transformation to Estimates of Inner Radii of Open Sets”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 10 (October 25, 2007): 1313–1321. Accessed March 29, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3390.