Bakker, R. J., van der Geer, C. A. J., Jaroszynski, D. A., van der Meer, A. F. G., Oepts, D., & van Amersfoort, P. W. (1993). Broad-Band Tunability of a Far-Infrared Free-Electron Laser. Journal of Applied Physics, 74, 1501-1509. https://doi.org/10.1063/1.354849 (Original work published 1993)
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