@article{ASUO_2009_XVII_2_a18,
     author = {
						Camelia Pop and Anania Aron},
     title = {
							{Drift-free} left invariant control system on {G4} with fewer controls than state variables
						},
     journal = {Analele Universit\u{a}\c{t}ii "Ovidius" Constan\c{t}a Seria Matematic\u{a}},
     publisher = {mathdoc},
     volume = {XVII},
     number = {2},
     year = {2009},
     url = {http://geodesic.mathdoc.fr/item/ASUO_2009_XVII_2_a18/}
}