@article {Guglielmi2014,
	title = {Null controllability of Grushin-type operators in dimension two},
	journal = {Journal of the European Mathematical Society},
	volume = {16},
	number = {1},
	year = {2014},
	pages = {67-101},
	author = {Beauchard, K. and Cannarsa, P. and Guglielmi, R.}
}