Virtual photon effects on classical chaos in a periodically kicked Rydberg atom system X. L. Zhang, C. H. Yuan, H. B. Huang and R. Ju Eur. Phys. J. D, 35 3 (2005) 541-545 Published online: 12 May 2005 DOI: 10.1140/epjd/e2005-00067-y