@article{MAN_1979__239_163217,
     author = {H.J. Hey and J. Ludwig},
     title = {Der {Satz} von {Helson-Reiter} f\"ur spezielle nilopotente {Lie-Gruppen.}},
     journal = {Mathematische Annalen},
     pages = {207--218},
     publisher = {mathdoc},
     volume = {239},
     year = {1979},
     zbl = {0377.22010},
     url = {http://geodesic.mathdoc.fr/item/MAN_1979__239_163217/}
}