Keitel, Christoph H. Division Prof. Dr. Christoph H. Keitel, MPI for Nuclear Physics, Max Planck Society;
http://iopscience.iop.org/0295-5075/48/5/533/ (Publisher version)
Walser, M. W., Szymanowski, C., & Keitel, C. H. (1999). Influence of spin-laser interaction on relativistic harmonic generation. Europhysics Letter, 48(5), 533-539. doi:10.1209/epl/i1999-00517-6.