@article{JRAM_1968__229_150844,
     author = {W. Degen},
     title = {Zur projektiven {Kinematik} der {H\"ullfl\"achen} gewisser {Hyperquadrikscharen.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {209--220},
     publisher = {mathdoc},
     volume = {229},
     year = {1968},
     zbl = {0173.23604},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1968__229_150844/}
}