@article{MZ_1936__40_168637,
     author = {U. Graf},
     title = {\"Uber einscharige in der linearen {Strahlenkongurenz} enthaltene {Regelfl\"achen} zweiten {Grades}},
     journal = {Mathematische Zeitschrift},
     pages = {671--682},
     publisher = {mathdoc},
     volume = {40},
     year = {1936},
     zbl = {62.0729.01},
     url = {http://geodesic.mathdoc.fr/item/MZ_1936__40_168637/}
}