@article{MZ_1931__33_168269,
     author = {W., Haack},
     title = {Affine {Differentialgeometrie} der parabolischen {Strahlensysteme}},
     journal = {Mathematische Zeitschrift},
     pages = {232--270},
     publisher = {mathdoc},
     volume = {33},
     year = {1931},
     zbl = {57.0958.03},
     url = {http://geodesic.mathdoc.fr/item/MZ_1931__33_168269/}
}