@article{CMH_1942__15_138803,
     author = {Walter Nef},
     title = {\"Uber die singul\"aren {Gebilde} der regul\"aren {Funktionen} einer {Quaternionenvariablen.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {144--174},
     publisher = {mathdoc},
     volume = {15},
     year = {1942},
     zbl = {0027.30902},
     url = {http://geodesic.mathdoc.fr/item/CMH_1942__15_138803/}
}