@book{BuergerSaupe1996,
  author    = {B{\"u}rger, Klaus and Saupe, Gabriele},
  title     = {Geos : Lehrbuch Geographie ; Sekundarstufe II ; Bd. 1 Wirtschaftsr{\"a}ume und Siedlungen},
  editor    = {Friese, Heinz W. and Motschmann, Siegfried},
  publisher = {Volk und Wissen},
  address   = {Berlin},
  pages     = {256 S.},
  year      = {1996},
  language  = {de}
}
@book{BuergerSaupe1996,
  author    = {B{\"u}rger, Klaus and Saupe, Gabriele},
  title     = {Geos : Lehrbuch Geographie ; Sekundarstufe II ; Bd. 2 Landschaften und Ressourcen},
  editor    = {Friese, Heinz W. and Motschmann, Siegfried},
  publisher = {Volk und Wissen},
  address   = {Berlin},
  pages     = {256 S.},
  year      = {1996},
  language  = {de}
}