@article{ELMA_1954__9_140611,
     author = {R. Sauer},
     title = {Elementargeometrische {Modelle} zur {Differentialgeometrie.}},
     journal = {Elemente der Mathematik},
     pages = {121--131},
     publisher = {mathdoc},
     volume = {9},
     year = {1954},
     zbl = {0056.14803},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1954__9_140611/}
}