@article{SpahnPetzschmannSchmidtetal.2001,
  author    = {Frank Spahn and Olaf Petzschmann and J{\"u}rgen Schmidt and Miodrag Sremcevic and Jan-Martin Hertzsch},
  title     = {About the viscosity of granular gases : the force-free case versus granular gases under Keplarian differential rotation},
  year      = {2001},
}