@article{MTA_2020_5_2_a14,
     author = {Pierpaolo Soravia},
     title = {A degenerate elliptic equation for second order controllability of nonlinear systems},
     journal = {Minimax theory and its applications},
     year = {2020},
     volume = {5},
     number = {2},
     zbl = {1453.93025},
     url = {http://geodesic.mathdoc.fr/item/MTA_2020_5_2_a14/}
}