S. SchreiberS. Lederer, "Lifetime of Cs2Te Cathodes Operated at the FLASH Facility", in Proc. 37th International Free Electron Laser Conference, Daejeon, Republic of Korea, August 2015, paper TUP042, pp. 464-467, ISBN: 978-3-95450-134-2, doi:10.18429/JACoW-FEL2015-TUP042, http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/tup042.pdf, 2015.