1. R. A. HAY, Geol. Soc. Am. Spec., Paper 85 (1965).
2. C. M. WARSHAW, R. ROY, Bull. Geol. Soc. Am., 72 (1961) 1455.
3. V. N. KUMOK, V. V. SEREBRENNIKOV, Russ. J. Inorg. Chem., 20 (1965) 9.
4. L. BERAK, IAEA, Vienna, May, 1969.
5. V. I. GRABENSHCHIKOVA, Y. P. DAVYDOV, Radiokhimiya, 7 (1965) 191.