@article{ELMA_1966__21_140824,
     author = {H. Zeitler},
     title = {S\"atze \"uber das {Sehnenviereck} in der sph\"arischen und hyperbolischen {Geometrie.}},
     journal = {Elemente der Mathematik},
     pages = {49--55},
     publisher = {mathdoc},
     volume = {21},
     year = {1966},
     zbl = {0135.39602},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1966__21_140824/}
}