@article{CC_2005_34_3_a10,
     author = {Jakubczyk, Bronis{\l}aw and Respondek, Witold},
     title = {Phase portraits of planar control-affine systems},
     journal = {Control and Cybernetics},
     pages = {819--847},
     publisher = {mathdoc},
     volume = {34},
     number = {3},
     year = {2005},
     zbl = {1167.93321},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CC_2005_34_3_a10/}
}