@article{JEMS_2014_16_1_a2,
     author = {Karine Beauchard and Piermarco Cannarsa and Roberto Guglielmi},
     title = {Null controllability of {Grushin-type} operators in dimension two},
     journal = {Journal of the European Mathematical Society},
     pages = {67--101},
     year = {2014},
     volume = {16},
     number = {1},
     doi = {10.4171/jems/428},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/428/}
}