SkrypnikI. I. “Regularity of Solutions of Degenerate Quasilinear Parabolic Equations (weighted Case)”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 48, no. 7, July 1996, pp. 972-88, https://umj.imath.kiev.ua/index.php/umj/article/view/5270.