Flach, S. Max Planck Institute for the Physics of Complex Systems, Max Planck Society;
Flach, S., Ivanchenko, M. V., Kanakov, O. I., & Mishagin, K. G. (2008). Periodic orbits, localization in normal mode space, and the Fermi-Pasta-Ulam problem. American Journal of Physics, 76(4-5), 453-459.