@article{GDZPPN002249286, title = {Ueber neue Focaleigenschaften der Fl\"achen 2. Grades}, journal = {Mathematische Annalen}, volume = {27}, year = {1886}, pages = {253-271}, zbl = {18.0755.02}, url = {http://dml.mathdoc.fr/item/GDZPPN002249286} }
Staude. Ueber neue Focaleigenschaften der Flächen 2. Grades. Mathematische Annalen, Tome 27 (1886) pp. 253-271. http://gdmltest.u-ga.fr/item/GDZPPN002249286/