@article{SpahnPetzschmannSchmidtetal.2001,
  author    = {Spahn, Frank and Petzschmann, Olaf and Schmidt, J{\"u}rgen and Sremcevic, Miodrag and Hertzsch, Jan-Martin},
  title     = {About the viscosity of granular gases : the force-free case versus granular gases under Keplarian differential rotation},
  isbn      = {3-540-41458-4},
  year      = {2001},
  language  = {en}
}
@article{SchollSpahnHertzschetal.1997,
  author    = {Scholl, H. and Spahn, Frank and Hertzsch, Jan-Martin and Katzorke, Ines},
  title     = {Simulation of collisions in planetary rings},
  year      = {1997},
  language  = {en}
}
@book{SpahnHertzschBrilliantov1995,
  author    = {Spahn, Frank and Hertzsch, Jan-Martin and Brilliantov, Nikolai V.},
  title     = {The role of particle collisions for the dynamics in planetary rings},
  series = {Preprint NLD},
  volume    = {14},
  journal   = {Preprint NLD},
  publisher = {Univ.},
  address   = {Potsdam},
  pages     = {23 S.},
  year      = {1995},
  language  = {en}
}
@phdthesis{Hertzsch1996,
  author    = {Hertzsch, Jan-Martin},
  title     = {{\"U}ber nichtelastische Kollisionen und ihren Einfluß auf die Strukturbildung in planetaren Ringen},
  pages     = {87 S., Ill.},
  year      = {1996},
  language  = {de}
}