@Article{ OttVit17, author = { Ottazzi, Alessandro and Vittone, Davide }, title = { On the codimension of the abnormal set in step two Carnot groups }, journal = { ESAIM Control Optim. Calc. Var. }, year = { 2019 }, doi = { http://dx.doi.org/10.1051/cocv/2018002 }, volume = { 25 }, pages = { }, URL = { http://cvgmt.sns.it/paper/3658/ }, note = { cvgmt preprint} }