1. The porous medium equation;Aronson,1986
2. The porous medium equation;Peletier,1981
3. Kamin S. & Vázquez J.E., Asymptotic behavior of solutions of the porous medium equation with changing sign, preprint.
4. An equation of diffusion type whose singularities depend on the sign of the solution;Béniean,1989
5. A generalized diffusion equation: radial symmetries and comparison theorems;Atkinson;J. math. Analysis Applic.,1983