I.P.S. Martin, R. Bartolini, D.J. Dunning, and N. Thompson,
   "Studies of Undulator Tapering for the CLARA FEL",
   in Proc. 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper TUP025, pp. 412-416,
    ISBN: 978-3-95450-134-2,
    doi:10.18429/JACoW-FEL2015-TUP025,
    http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/tup025.pdf, 2015.