@article{ELMA_1975__30_141161,
     author = {W. Wunderlich},
     title = {Elementarer {Zugang} zur hyperbolischen {Geometrie.}},
     journal = {Elemente der Mathematik},
     pages = {103--108},
     year = {1975},
     volume = {30},
     zbl = {0309.50009},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1975__30_141161/}
}