@article{MAN_1947__120_160163,
     author = {Ott-Heinrich Keller},
     title = {Zur {Theorie} der ebenen {Ber\"uhrungstransformationen} {I.} {Teil.} {Fundamentalkurven} ebener {Ber\"uhrungstransformationen}},
     journal = {Mathematische Annalen},
     pages = {650--675},
     publisher = {mathdoc},
     volume = {120},
     year = {1947},
     zbl = {0032.18602},
     url = {http://geodesic.mathdoc.fr/item/MAN_1947__120_160163/}
}