@article{GruberVossBalderjahnetal.2007,
  author    = {Gruber, Thorsten and Voss, Roediger and Balderjahn, Ingo and Reppel, Alexander},
  title     = {Online Laddering},
  isbn      = {978-3-8349-0229-0},
  year      = {2007},
  language  = {de}
}