V. Hafner, and F. Kaplan. Proceedings of the Third International Symposium on Imitation in animals and artifacts, page 48--53. Herderfordshire, UK, (2005)
L. Olsson, C. Nehaniv, and D. Polani. Proceedings of the 6th IEEE International Symposium on Computational Intelligence in Robotics and Automation (CIRA 2005), Espoo, Finland, IEEE Computer Society Press, (2005)