@article{MZ_1977__154_172527,
     author = {Kay S\"orensen},
     title = {Inzidenzgruppen der {Ordnung} 3.},
     journal = {Mathematische Zeitschrift},
     pages = {239--242},
     publisher = {mathdoc},
     volume = {154},
     year = {1977},
     zbl = {0365.50005},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__154_172527/}
}