@article{MZ_1927__26_167921,
     author = {A. Winternitz},
     title = {Beweis f\"ur die {Invarianz} des ebenen {Gebiets}},
     journal = {Mathematische Zeitschrift},
     pages = {165--169},
     publisher = {mathdoc},
     volume = {26},
     year = {1927},
     zbl = {53.0564.01},
     url = {http://geodesic.mathdoc.fr/item/MZ_1927__26_167921/}
}