1. P. Bukovec undL. Golič, Vest. Slov. Kem. Drus.22, 19 (1975).
2. F. Zambonini undS. Restaino, Atti Accad. Lincei9, 131 (1929).
3. S. Restaino, Atti Accad. Lincei20, 192 (1934).
4. L. L. Zajceva, V. S. Pljaščenko, M. I. Konarev, L. V. Lipis undN. T. Čebotarev, J. Neorg. Chim.12, 677 (1967).
5. L. D. Iskhakova, V. E. Plyuschev undN. D. Berlin, J. Neorg. Chim. [russ.]18, 694 (1973); Chem. Abstr.78, 131 506 c (1973).