@article{MAN_1969__180_161792,
     author = {G. FREI},
     title = {Orientierungsfunktionen.},
     journal = {Mathematische Annalen},
     pages = {60--74},
     publisher = {mathdoc},
     volume = {180},
     year = {1969},
     url = {http://geodesic.mathdoc.fr/item/MAN_1969__180_161792/}
}