@article{AIHPC_1996__13_6_635_0,
     author = {Agrachev, A. A. and Sarychev, A. V.},
     title = {Abnormal sub-riemannian geodesics : {Morse} index and rigidity},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {635--690},
     publisher = {Gauthier-Villars},
     volume = {13},
     number = {6},
     year = {1996},
     mrnumber = {1420493},
     zbl = {0866.58023},
     language = {en},
     url = {http://archive.numdam.org/item/AIHPC_1996__13_6_635_0/}
}