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\bibitem{Gao_etal2006} Gao, J. R., Hiajenius, M., Yang, Z. Q., Klapwijk, T. M., Miao, W., Shi, S. C., et al. (2006). Direct comparison of the sensitivity of a spiral and a twin-slot antenna coupled HEB mixer at 1.6 THz. In \textit{Proc. 17$^{th}$ Int. Symp. Space Terahertz Technol.} (pp. 59--62).

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