Marcus, M., and A. E. Shishkov. “Propagation of Strong Singularities in Semilinear Parabolic Equations With Degenerate Absorption”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, vol. 16, no. 3, Sept. 2016, pp. 1019-47, doi:10.2422/2036-2145.201502_006.