https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.264801 (Publisher version)
Labat, M., Joly, N., Bielawski, S., Szwaj, C., Bruni, C., & Couprie, M. E. (2009). Pulse Splitting in Short Wavelength Seeded Free Electron Lasers. Physical Review Letters, 103: 264801. doi:10.1103/PhysRevLett.103.264801.