Ivasyshen, S. D., and V. A. Litovchenko. “Cauchy Problem for One Class of Degenerate Parabolic Equations of Kolmogorov Type With Positive Genus”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 61, no. 8, Aug. 2009, pp. 1066-87, https://umj.imath.kiev.ua/index.php/umj/article/view/3081.