H. Zen, T. Kii, R. Kuroda, K. Masuda, H. Ohgaki, S. Suphakul, and Y. Taira, "MIR-FEL Oscillator Lasing by Photocathode Operation of LaB6 Thermionic Cathode in KU-FEL", presented at the 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper MOA01, unpublished.