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\bibitem{Ryabchun_etal2007} Ryabchun S, Tong C-yu E, Blundell R, Kimberk R, Gol{\textquoteright}tsman G. Stabilisation of a terahertz hot-electron bolometer mixer with microwave feedback control. In: Proc. 18$^{th}$ Int. Symp. Space Terahertz Technol.; 2007. p. 193--8.

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