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\bibitem{Schwaab_etal1999} Schwaab GW, H{\"u}bers H-W, Schubert J, Erichsen P, Gol{\textquoteright}tsman G, Semenov A, et al. A high resolution spectrometer for the investigation of molecular structures in the THZ range. In: Proc. 10$^{th}$ Int. Symp. Space Terahertz Technol.; 1999. p. 530--8.

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