%\cite{Chaisueb:FEL2015-WEP062} \bibitem{Chaisueb:FEL2015-WEP062} N.~ChaisuebS.~Rimjaem, \textquotedblleft{Study on Undulator Radiation from Femtosecond Electron Bunches}\textquotedblright, % in \emph{Proc. FEL2015}, WEP062, pp. 702--706, % in \emph{Proc. FEL2015}, Daejeon, Republic of Korea, August 2015, paper WEP062, pp. 702--706, in \emph{Proc. 37th International Free Electron Laser Conference (FEL2015)}, Daejeon, Republic of Korea, August 2015, paper WEP062, pp. 702--706, ISBN: 978-3-95450-134-2, \url{http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/wep062.pdf}, doi:10.18429/JACoW-FEL2015-WEP062, 2015.