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\bibitem{Yagoubov_etal1999} Yagoubov P, Kroug M, Merkel H, Kollberg E, H{\"u}bers H-W, Schubert J, et al. NbN hot electron bolometric mixers at frequencies between 0.7 and 3.1 THz. In: Proc. 10$^{th}$ Int. Symp. Space Terahertz Technol.; 1999. p. 238--46.

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