@article{JRAM_1883__95_148566,
     author = {F. Rudio},
     title = {Zur {Theorie} der {Fl\"achen,} deren {Kr\"ummungsmittelpunktsfl\"achen} confocale {Fl\"achen} zweiten {Grades} sind.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {240--246},
     publisher = {mathdoc},
     volume = {95},
     year = {1883},
     zbl = {15.0625.01},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1883__95_148566/}
}