Zhang, W., Jiang, L., Lin, Z. H., Yao, Q. J., Li, J., Shi, S. C., et al. (2005). Development of a quasi-optical NbN superconducting HEB mixer. In _Proc. 16<sup>th</sup> Int. Symp. Space Terahertz Technol._ (pp. 209&ndash;213).