@article{JRAM_1938__178_150033,
     author = {G. Haenzel and F. Reutter},
     title = {Die {Geometrie} der linearen {Strahlenkongruenz.} {III.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {229--252},
     publisher = {mathdoc},
     volume = {178},
     year = {1938},
     zbl = {0018.23104},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1938__178_150033/}
}