@article{AIHPC_2001__18_4_459_0,
     author = {Montgomery, Richard and Zhitomirskii, Michail},
     title = {Geometric approach to {Goursat} flags},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {459--493},
     publisher = {Elsevier},
     volume = {18},
     number = {4},
     year = {2001},
     mrnumber = {1841129},
     zbl = {1013.58004},
     language = {en},
     url = {http://www.numdam.org/item/AIHPC_2001__18_4_459_0/}
}