S. Huang, Y. Ding, Z. Huang, and G. Marcus,
   "Generating Femtosecond to Sub-Femtosecond X-Rays with a Modulated Chirped Beam in a Self-Seeded FEL",
   presented at the 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper TUB03, unpublished.