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\bibitem{Ekstroem_etal1995} Ekstr{\"o}m H, Karasik B, Kollberg E, Gol{\textquoteright}tsman G, Gershenzon E. 350 GHz NbN hot electron bolometer mixer. In: Proc. 6$^{th}$ Int. Symp. Space Terahertz Technol.; 1995. p. 269--83.

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