BoldovskayaO. M. “Removability of an Isolated Singularity of Solutions of the Neumann Problem for Quasilinear Parabolic Equations With Absorption That Admit Double Degeneration”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 7, July 2010, pp. 894–912, https://umj.imath.kiev.ua/index.php/umj/article/view/2923.