1. Trew, V.C.G.: Trans. Faraday Soc. 32 (1936) 1658.
2. Kido, K.: Rept. Yokohama Tech. Coll. Jpn. 2 (1934) 233.
3. Pacault, A., Stoltz, M.: Compt. Rend. 228 (1949) 74.
4. Pascal, P., Band, P.: Traite de Chimie Minerale 6 (1934) 441.
5. Perakis, N., Capatos, L.: J. Phys. Radium 6 (1935) 462