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\bibitem{Ekstroem_etal1994} Ekstr{\"o}m, H., Karasik, B., Kollberg, E., \& Yngvesson, K. S. (1994). Investigation of a superconducting hot electron mixer. In \textit{Proc. 5$^{th}$ Int. Symp. Space Terahertz Technol.} (pp. 169--188).

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