Bakhtin , A. K., and Ya. V. Zabolotnii. “Estimates of Products of Some Powers of Inner Radii for Multiconnected Domains”. Ukrains’kyi Matematychnyi Zhurnal, vol. 73, no. 9, Sept. 2021, pp. 1155-69, https://doi.org/10.37863/umzh.v73i9.6682.