@article{JRAM_1979__0311_0312_152168,
     author = {G\"unther Frei and Claude Levesque},
     title = {Independent systems of units in certain algebraic number fields.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {116--144},
     publisher = {mathdoc},
     volume = {0311_0312},
     year = {1979},
     zbl = {0409.12006},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1979__0311_0312_152168/}
}