@misc{Schäfer_Dietrich_(1845–1929)_Sprachenkarte_1910,
 author={Schäfer, Dietrich (1845–1929)},
 copyright={Public Domain},
 address={Berlin},
 howpublished={online},
 year={1910},
 publisher={Verlag Karl Curtius},
 language={ger},
 title={Sprachenkarte der Deutschen Ostmarken},
 keywords={linguistic maps, population maps, Germany, 20th century},
}