E. Ferrari, E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, D. Gauthier, \emph{et al.},
   "Influence of a Non-Uniform Longitudinal Heating on High Brightness Electron Beams for FEL",
   presented at the 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper TUB04, unpublished.