Markish, A. A., R. R. Salimov, and E. A. Sevost’yanov. “On the Lower Estimate of the Distortion of distance for One Class of Mappings”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 70, no. 11, Nov. 2018, pp. 1553-62, https://umj.imath.kiev.ua/index.php/umj/article/view/1659.