1. V. V. Antonov-Romanovskii, V. L. Levshin, Z. L. Morgenshtern, and Z. A. Trapeznikova, Dokl. Akad. Nauk SSSR 54(1), 19 (1946).
2. V. V. Antonov-Romanovskii, Dokl. Akad. Nauk SSSR 58(5), 771 (1947).
3. Z. L. Morgenshtern, Dokl. Akad. Nauk SSSR 58(5), 783 (1947).
4. V. L. Levshin, Zh. Eksp. Teor. Fiz., No. 1, 82 (1948).
5. J. Lambe and C. Klick, Phys. Rev. 98(4), 909 (1955).