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\bibitem{Kroug_etal2001} Kroug M, Cherednichenko S, Choumas M, Merkel H, Kollberg E, H{\"u}bers H-W, et al. HEB quasi-optical heterodyne receiver for THz frequencies. In: Proc. 12$^{th}$ Int. Symp. Space Terahertz Technol. San Diego, CA, USA; 2001. p. 244--52.

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