M. Haruno, D. Wolpert, and M. Kawato. Excepta Medica International Coungress Series, 1250, page 575-590. Amsterdam, The Netherlands, Elsevier Science B.V., (2003)
H. Cruse, U. Steinkühler, and C. Burkamp. From Animals to Animats 5: Proceedings of the Fifth International
Conference on Simulation of Adaptive Behavior, (1998)