@article{Moeller1999,
  author    = {M{\"o}ller, Rainer},
  title     = {Mit Karten unterwegs},
  year      = {1999},
  language  = {de}
}
@article{Moeller1999,
  author    = {M{\"o}ller, Rainer},
  title     = {Natur und Umwelt auf der Spur},
  year      = {1999},
  language  = {de}
}
@article{Moeller1999,
  author    = {M{\"o}ller, Rainer},
  title     = {Im Land Brandenburg},
  year      = {1999},
  language  = {de}
}
@article{Moeller1999,
  author    = {M{\"o}ller, Rainer},
  title     = {Im Land Brandenburg},
  year      = {1999},
  language  = {de}
}