@article{KoebRiedel2007,
  author    = {K{\"o}b, Ansgar and Riedel, Peter},
  title     = {Vorwort},
  isbn      = {3-7705-4202-9},
  year      = {2007},
  language  = {de}
}
@article{KoebRiedel2005,
  author    = {K{\"o}b, Ansgar and Riedel, Peter},
  title     = {Vorwort},
  isbn      = {3-7705-4036-0},
  year      = {2005},
  language  = {de}
}