Diaz, J. I., and J. Hernández. “Linearized Stability for Degenerate and Singular Semilinear and Quasilinear Parabolic Problems: The Linearized Singular Equation”. Topological Methods in Nonlinear Analysis, vol. 54, no. 2B, Nov. 2019, pp. 937-66, https://apcz.umk.pl/TMNA/article/view/TMNA.2019.091.