1. Dadieu and Kohirausch, Ber., 63, 251; 1930.
2. F. Rasetti, NATURE, 123, 205; 1929.
3. cf. Sidgwick, "Electronic Theory of Valency", p. 216.
4. Dadieu and Schneider, Akad. Anzeiger der Akad. der Wiss., Wien. Oct. 15, 1931.
5. Sutton and Bentley, NATURE, 130, 314; 1932.