Sami Haddadin Tim Laue Udo Frese Sebastian Wolf Alin Albu-Schäffer Gerd Hirzinger Kick it with elasticity: Safety and performance in human-robot soccer. 761-775 2009 57 Robotics and Autonomous Systems 8 http://dx.doi.org/10.1016/j.robot.2009.03.004 db/journals/ras/ras57.html#HaddadinLFWAH09