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\bibitem{Yagoubov_etal1999} Yagoubov, P., Kroug, M., Merkel, H., Kollberg, E., H{\"u}bers, H. - W., Schubert, J., et al. (1999). NbN hot electron bolometric mixers at frequencies between 0.7 and 3.1 THz. In \textit{Proc. 10$^{th}$ Int. Symp. Space Terahertz Technol.} (pp. 238--246).

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