@Article{ AgrRizSil13, author = { Agrachev, Andrei and Rizzi, Luca and Silveira, Pavel }, title = { On conjugate times of LQ optimal control problems }, journal = { Journal of Dynamical and Control Systems }, year = { 2013 }, doi = { 10.1007/s10883-014-9251-6 }, pages = { }, URL = { http://cvgmt.sns.it/paper/2277/ }, note = { cvgmt preprint} }