1. S. F. Bureiko, G. S. Denisov, and K. G. Tokhadze, ?Proton exchange in hydrogen-bond systems,? in: Molecular Spectroscopy [in Russian], No. 4, Izd. Leningrad. Univ., Leningrad (1977).
2. R. F. Hudson, Structure and Mechanism in Organophosphorus Chemistry, Academic Press, New York (1965).
3. G. I. Derkach, I. N. Zhmurova, A. V. Kirsanov, V. I. Shevchenko, and A. S. Shtepanek, Phosphazo Compounds [in Russian], Naukova Dumka, Kiev (1965).
4. S. Patai, The Chemistry of the Carbon-Nitrogen Double Bond, Wiley-Interscience, New York (1970).
5. A. E. Lutskii, L. I. Samarai, L. A. Kochergina, A. V. Shepel', Z. A. Shevchenko, G. I. Derkach, É. S. Kozlov, and B. S. Drach, ?The participation of the phosphorus d orbital in ?-bond formation and in conjugation with ?-electron systems. II. Dipole moments of several phosphazo compounds,? Zh. Obshch. Khim., 37, No. 9, 2042?2046 (1967).