@misc{_Übersichtskarte_[ca,
 copyright={Public Domain},
 address={Berlin},
 howpublished={online},
 year={[ca 1939]},
 publisher={Gea Verlag},
 publisher={Berliner Lithographisches Institut},
 language={ger},
 title={Übersichtskarte 1:1 000 000 : Ostblatt},
 keywords={political-administrative maps, Poland, Eastern Europe},
}