1. P. D. McWane, Nature 211, 1081 (1966).
2. A. A. Borshch, M. S. Brodin, V. I. Volkov, and V. V. Ovchar, Kvantovaya Élektron. 2, 602 (1975) [Sov. J. Quantum Electron. 5, 340 (1975)].
3. A. A. Borshch, M. S. Brodin, V. I. Volkov, and N. N. Krupa, Zh. Tekh. Fiz. 48, 2273 (1978) [Sov. Phys. Tech. Phys. 23, 1356 (1978)].
4. N. N. Krupa, N. Ya. Nedbaev, P. A. Petrenko, and A. A. Statsenko, USSR Author’s Certificate No. 10901145, International Patent Classification (IPC) 3 G 02 1/37, application dated June 18, 1982, published January 3, 1984.
5. V. T. Bagatskii, N. N. Krupa, and V. I. Lomakin, USSR Author’s Certificate No. 1259844, International Patent Classification (IPC) G 02 F 1/09, application dated August 16, 1984, published July 29, 1985.