@article{MZ_1932__35_168378,
     author = {W., Haack},
     title = {Zylindrische {Strahlensysteme}},
     journal = {Mathematische Zeitschrift},
     pages = {660--683},
     publisher = {mathdoc},
     volume = {35},
     year = {1932},
     zbl = {0005.02402},
     url = {http://geodesic.mathdoc.fr/item/MZ_1932__35_168378/}
}