@article{AIHPC_2010__27_3_793_0,
     author = {Agrachev, A.A. and Boscain, U. and Charlot, G. and Ghezzi, R. and Sigalotti, M.},
     title = {Two-dimensional {almost-Riemannian} structures with tangency points},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {793--807},
     publisher = {Elsevier},
     volume = {27},
     number = {3},
     year = {2010},
     doi = {10.1016/j.anihpc.2009.11.011},
     mrnumber = {2629880},
     zbl = {1192.53029},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1016/j.anihpc.2009.11.011/}
}