G.  Grioli, Catalano, M. G., Garabini, M., Bonomo, F., Serio, A., Salaris, P., Belo, F. A. W., Mancini, M., Bicchi, A., and Passaglia, A., ?Variable stiffness actuators: muscles for the next generation of robots?, in Automatica.it 2011, Pisa, Italy, 2011.