@misc{Joel_M._Oberschlesien,
 author={Joel, M. and Guckel, Marg. and Vogt, Maria and Drechsler, Hel.},
 address={[S.l.]},
 howpublished={online},
 publisher={[s.n.]},
 language={ger},
 title={Oberschlesien},
 keywords={Śląsk Górny, historia, mapy, kartografia, średniowiecze, 18 w., 19 w., 20 w.},
}