A stationary Stefan problem with convection and nonlinear diffusion. Urbano, José Miguel — 1995 Portugaliae Mathematica
Harnack's estimates: positivity and local behavior of degenerate and singular parabolic equations. DiBenedetto, Emmanuele; Gianazza, Ugo; Safonov, Mikhail; Urbano, José Miguel; Vespri, Vincenzo — 2007 Boundary Value Problems [electronic only]