Nonlinear and Optimal Control Theory [electronic resource] : Lectures given at the C.I.M.E. Summer School held in Cetraro, Italy June 19–29, 2004 / by Andrei A. Agrachev, A. Stephen Morse, Eduardo D. Sontag, Héctor J. Sussmann, Vadim I. Utkin ; edited by Paolo Nistri, Gianna Stefani.