F.-J. Decker, S. Gilevich, Z. Huang, H. Loos, A. Marinelli, C.A. Stan, \emph{et al.}, "Two Bunches with ns-Separation with LCLS", in Proc. 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper WEP023, pp. 634-638, ISBN: 978-3-95450-134-2, doi:10.18429/JACoW-FEL2015-WEP023, http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/wep023.pdf, 2015.