@article{JRAM_1969__237_150948,
     author = {G. Bol},
     title = {Zur {M\"obius-Geometrie} der {Kugelkongruenzen.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {109--165},
     publisher = {mathdoc},
     volume = {237},
     year = {1969},
     zbl = {0175.48302},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1969__237_150948/}
}