@article{BAG_1985__20_138317,
     author = {J. Hilgert and K.H. Hofmann and J.D. Lawson},
     title = {Controllability of systems on a nilpotent {Lie} group},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {185--190},
     publisher = {mathdoc},
     volume = {20},
     year = {1985},
     zbl = {0579.22010},
     url = {http://geodesic.mathdoc.fr/item/BAG_1985__20_138317/}
}