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\bibitem{Hajenius_etal2004} Hajenius M, Baselmans JJA, Gao JR, Klapwijk TM, de Korte 2 PAJ, Voronov B, et al. Increased bandwidth of NbN phonon cooled hot electron bolometer mixers. In: Proc. 15$^{th}$ Int. Symp. Space Terahertz Technol.; 2004. p. 381--6.

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