“…Furthermore, the methods used were rather ad hoc [HM06,HM11]. On the other hand, systematic results close to the setting of this paper were given previously in [AS05, AS06, Shi07, Shi08, Shi10, Ner10,Ner15]. While related, our results more directly extend the geometric control theory work of Jurdjevic and Kupka [JK81, JK85,Jur97].…”