BazaliiB. V., and TedeevA. F. 1995. “Method for Symmetrization and Estimation of Solutions of the Neumann Problem for the Equation of a Porous Medium in Domains With Noncompact Boundary for Infinitely Increasing Time”. Ukrains’kyi Matematychnyi Zhurnal 47 (2), 147–157. https://umj.imath.kiev.ua/index.php/umj/article/view/5398.