@article{MAN_1898__50_157889,
     author = {Otto Staude},
     title = {Die algebraischen {Grundlagen} der {Focaleigenschaften} der {Fl\"achen} 2. {Ordnung}},
     journal = {Mathematische Annalen},
     pages = {398--428},
     publisher = {mathdoc},
     volume = {50},
     year = {1898},
     zbl = {29.0538.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1898__50_157889/}
}