1. ISHII: ”Locomotion of a Quadruped Robot Using CPG”, Neural Networks. Proceedings IEEE International Joint Conference on, Volume 4 (2004)
2. ”Neurophysiology of Locomotor Automatism”;Shink;Physiol.Review,1976
3. ”On relaxation oscillations”;van der Pol;Philos. Mag.,1926
4. Nohara, B.T. and Arimoto, A.: ”Asymptotically Orbitally Stability of Coupled van der Pol equations”, preprint (2007)
5. ”Perturbation Methods”;Nayfeh,1973