Huseynov, S. T. “Hölder Continuity and the Harnack Inequality for the Solutions of an elliptic equation Containing the $p$ -Laplacian and Uniformly Degenerating in a Part of the Domain”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 12, Dec. 2017, pp. 1596-04, https://umj.imath.kiev.ua/index.php/umj/article/view/1806.