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\bibitem{Schubert_etal1999} Schubert J, Semenov A, Gol{\textquoteright}tsman G, H{\"u}bers H-W, Schwaab G, Voronov B, et al. Noise temperature and sensitivity of a NbN hot-electron mixer at frequencies from 0.7 THz to 5.2 THz. In: Proc. 10$^{th}$ Int. Symp. Space Terahertz Technol.; 1999. p. 190--9.

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