@misc{_Shell_[ca,
 copyright={Public Domain},
 address={[S.l.]},
 howpublished={online},
 year={[ca 1924]},
 publisher={[s.n.]},
 language={ger},
 title={Shell Straßenkarte. Nr. 14, Oberschlesien},
 keywords={road maps, Upper Silesia},
}