1. V.S. Ergakov, M.A. Moiseev, and V.I. Khizhnyak, Radiotekh. Elektron. (in Russian), 23(12), 2591 (1978).
2. G.S. Nusinovich, Radiophys. Quantum Electron., 18(11), 1246 (1975).
3. A.H. McCurdy, C. Armstrong, Phys. Fluids B: Plasma Phys., 3(1), 212 (1991).
4. G.S. Nusinovich, Radio Eng. Electron. Phys., 22(10), 151 (1977).
5. J. Jelonnek and K. Schuenemann, Proc. 21st Int. Conf. Infr. Millim. Waves, AM7 (1996).