@Article{ BarBosGau12, author = { Barilari, Davide and Boscain, Ugo and Gauthier, Jean-Paul }, title = { On 2-step, corank 2 nilpotent sub-Riemannian metrics }, journal = { SIAM, Journal of Control and Optimization }, year = { 2012 }, volume = { 50 }, number = { 1 }, pages = { 559-582 }, URL = { http://cvgmt.sns.it/paper/1799/ }, note = { cvgmt preprint} }