1. A.Acker - B.Kawohl,Remarks on quenching, Nonlinear Analysis - TMA (to appear).
2. A. Acker -W. Walter,On the global existence of solutions of parabolic equations with a singular nonlinear term, Nonlinear Analysis, TMA,2 (1978), pp. 499–504.
3. A. Acker -W. Walter,The quenching problem for nonlinear parabolic equations, Lecture Notes in Mathematics,564, Springer-Verlag, New York, 1976.
4. C. Bandle -C.-M. Brauner,Singular perturbation method in a parabolic problem with free boundary, inProc. BAIL IVth Conference, Novosibirsk, Boole Press, Dublin 1987.
5. B.Gidas -Wei-Ming Ni - L.Nirenberg,Symmetry and related properties via the maximum principle, Comm. Math. Phys.,68 (1979).