1. Human and Mills, Nature, 158, 876 (1946).
2. Carré, and Libermann, C.R. Acad. Sci. Paris, 199, 1422 (1934).
3. Gerrard and French, Nature, 159, 263 (1947).
4. Darzens, C.R. Acad. Sci. Paris, 152, 1314 (1912).
5. Libermann, Ion, 4, 40–41, 813 (Madrid, 1944).