1. R. B. Kieburts and A. Ishimaru, IRE Trans.,AP-9, no. 6, 606, 1961.
2. L. L. Oh, C. D. Lunden, and C. Chion, Microwave J.,7, no. 4, 62, 1964.
3. B. A. Panchenko, Radiotekhnika i elektronika,12, no. 4, 721, 1967.
4. I. B. Levinson and P. Sh. Fridberg, Radiotekhnika i elektronika,10, no. 2, 260, 1965.
5. Ya. N. Fel'd, ZhTF,17, no. 9, 1051, 1947.