1. M. B. Vinogradova, O. V. Rudenko, and A. P. Sukhorukov, The Wave Theory (Nauka, Moscow, 1979) [in Russian].
2. A. Sommerfeld, Ann. Phys. (New York) 44, 177 (1914).
3. L. Brillouin, Ann. Phys. (New York) 44 (10), 203 (1914).
4. P. A. Armand, J. Commun. Technol. Electron. 48, 957 (2003).
5. G. M. Strelkov, J. Commun. Technol. Electron. 43, 864 (1998).