1. I. A. Gilinskii, DAN SSSR,134, no. 5, 1055, 1960.
2. V. K. Yulpatov, Report read at the 4th All-Union Radioelectronic Conference of MVSSO SSSR, Khar'kov, October 1960.
3. W. L. Dickson, C. C. Johnson, and R. W. Grow, Proc. IRE,49, no. 11, 1696, 1961.
4. V. A. Zhurakhovskii, Radiotekhnika i elektronika,9, no. 8, 1527, 1964.
5. A. A. Kuraev and Yu. N. Kuvshinov, collection: Problems of Microwave Electronics [in Russian], izd. SGU, no. 1, p. 118, 1964.