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\bibitem{Ynvesson+Kollberg1999} Ynvesson, K. S., \& Kollberg, E. L. (1999). Optimum receiver noise temperature for NbN HEB mixers according to standard model. In \textit{Proc. 10$^{th}$ Int. Symp. Space Terahertz Technol.} (pp. 566--582).

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