Yazoubov, P., Kroug, M., Merkel, H., Kollberg, E., Gol'tsman, G., Lipatov, A., et al. (1998). Quasioptical NbN phonon-cooled hot electron bolometric mixers with low optimal local oscillator power. In _Proc. 9<sup>th</sup> Int. Symp. Space Terahertz Technol._ (pp. 131&ndash;140).