1. T. Gramstad et al., Spectrochim. Acta, 19, 1363, 1391 (1963); 21, 1073 (1965); 22, 1681 (1966); 28A, 1405 (1972).
2. R. Hudson, Structure and Mechanism in Organophosphorus Chemistry, Academic (1965).
3. Yu. Ya. Borovikov, E. V. Ryl'tsev, I. E. Boldeskul, N. G. Feshchenko, Yu. P. Makovetskii, and Yu. P. Egorov, Zh. Obshch. Khim., 40, 1957 (1970).
4. I. E. Boldeskul, Yu. P. Egorov, Yu. P. Makovetskii, E. V. Ryl'tsev, and N. G. Feshchenko, Zh. Prikl. Spektrosk., 16, 859 (1972).
5. J. E. Mrocher, J. J. Richard, and C. B. Bank, J. Inorg. Nucl. Chem., 27, 625 (1965).