@misc{Ptolemaeus_Claudius_Des_1913,
 author={Ptolemaeus, Claudius},
 address={Leipzig},
 howpublished={online},
 year={1913},
 publisher={Verlag von B. G. Teubner},
 language={ger},
 type={text},
 title={Des Claudius Ptolemäus Handbuch der Astronomie. Bd. 2},
 keywords={Ptolemaic system, mathematical astronomy},
}