Aldashev, S. A., and E. T. Kitaibekov. “Well-Posedness of the Dirichlet Problem in a Cylindrical Domain for Three-Dimensional Elliptic Equations With Degeneration of Type and Order”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 9, Sept. 2017, pp. 1270-4, http://umj.imath.kiev.ua/index.php/umj/article/view/1778.