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%\cite{wu:fel2019-tud01}
\bibitem{wu:fel2019-tud01}
Y.K. Wu, S.V. Benson, H. Hao, P. Liu, S.F. Mikhailov, V. Popov, and \emph{et al.},
% Y.K. Wu, S.V. Benson, H. Hao, P. Liu, S.F. Mikhailov, V. Popov, and J. Yan,
% Y.K. Wu \emph{et al.},
\textquotedblleft{Generating Orbital Angular Momentum Beams in an FEL Oscillator}\textquotedblright,
% --- abbreviated form (UNpublished paper) - JACoW template Feb 2018 ---
presented at FEL'19, Hamburg, Germany, Aug. 2019, paper TUD01, unpublished.