@misc{Wittstein_Theodor_(1816–1894)_Lehrbuch_1873,
 author={Wittstein, Theodor (1816–1894)},
 copyright={Public Domain},
 address={Hannover},
 howpublished={online},
 year={1873},
 publisher={Hahn'nche Hofbuchhandlung},
 language={ger},
 title={Lehrbuch der Elementar-Mathematik. 2 Bd., 1 Abt., Ebene Trigonometrie},
 type={Text},
}