Maslennikov SN, Finkel MI, Antipov SV, Polyakov SL, Zhang W, Ozhegov R, et al. Spiral antenna coupled and directly coupled NbN HEB mixers in the frequency range from 1 to 70 THz. In: Proc. 17^th Int. Symp. Space Terahertz Technol. Paris, France; 2006. p. 177–9.