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3. The porous medium equation;Aronson,1986
4. M. Bertsch and D. Hilhorst, The interface between regions where u < 0 and u > 0 in the porous medium equation, submitted for publication.
5. On a class of similarity solutions of the equation ut = (¦u¦m − 1 ux)x with m > − 1;van Duijn;IMA J. Appl. Math.,1988