@article{MAN_1954__127_160382,
     author = {W. Klingenberg},
     title = {Eine {Begr\"undung} der hyperbolischen {Geometrie.}},
     journal = {Mathematische Annalen},
     pages = {340--356},
     publisher = {mathdoc},
     volume = {127},
     year = {1954},
     zbl = {0055.13803},
     url = {http://geodesic.mathdoc.fr/item/MAN_1954__127_160382/}
}