@article{10_1007_s10587_015_0214_1,
     author = {Littig, Samuel and Voigt, J\"urgen},
     title = {Porous medium equation and fast diffusion equation as gradient systems},
     journal = {Czechoslovak Mathematical Journal},
     pages = {869--889},
     publisher = {mathdoc},
     volume = {65},
     number = {4},
     year = {2015},
     doi = {10.1007/s10587-015-0214-1},
     mrnumber = {3441322},
     zbl = {06537697},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10587-015-0214-1/}
}