@article{MAN_1935__111_159760,
     author = {R. Sauer},
     title = {Infinitesimale {Verbiegungen} zueinander projektiver {Fl\"achen.}},
     journal = {Mathematische Annalen},
     pages = {71--82},
     publisher = {mathdoc},
     volume = {111},
     year = {1935},
     zbl = {0010.37402},
     url = {http://geodesic.mathdoc.fr/item/MAN_1935__111_159760/}
}