SamsoniyaZ. V., and SamkharadzeI. G. “On Quasiconformal Mappings Corresponding to the Beltrami Equation”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 51, no. 10, Oct. 1999, pp. 1391–1397, https://umj.imath.kiev.ua/index.php/umj/article/view/4738.