1. N. F. Mott, Adv. Phys.,13, No. 51 (1964).
2. D. W. Jones, Phil. Mag.,9, 709 (1964).
3. K. A. Chao and G. S. Ansell, J. Appl. Phys.,41, 417 (1970).
4. T. V. Simonishvili, Dokl. Akad. Nauk SSSR,196, 645 (1971).
5. D. Wood, R. Jaffe, and E. Salkovitz, in: High-Melting Metallic Materials for Space Technology [Russian translation], Mir, Moscow (1966), p. 315.