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\bibitem{Semenov_etal2002} Semenov, A., H{\"u}bers, H. - W., Richter, H., Birk, M., Krocka, M., Mair, U., et al. (2002). Performance of terahertz heterodyne receiver with a superconducting hot-electron mixer. In \textit{Proc. 13$^{th}$ Int. Symp. Space Terahertz Technol.} (pp. 229--234).

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