A.  Bicchi, Bavaro, M., Boccadamo, G., Carli, D. D., Filippini, R., Grioli, G., Piccigallo, M., Rosi, A., Schiavi, R., Sen, S., and Tonietti, G., ?Physical Human-Robot Interaction: Dependability, Safety, and Performance?, in Proc. 10th Intl. Workshop Advanced Motion Control, 2008, pp. 9-14. 

A.  Bicchi, Tonietti, G., Bavaro, M., and Piccigallo, M., ?Variable Stiffness Actuators for Fast and Safe Motion Control?, in Proceedings of the International Symposium on Robotics Research, B.  Siciliano, Khatib, O., and Groen, F., Eds. Springer Verlag, 2003.