1. de la Mare, P. B. D., Dunn, T. M., and Harvey, J. T., J. Chem. Soc., 923 (1957).
2. Grovenstein, E., jun., and Kilby, D. C., J. Amer. Chem. Soc., 79, 2972 (1957).
3. Zollinger, H., Angew. Chemic, 70, 204 (1958).
4. Kurakin, A. N., and Shilov, E. A., Ukrainian Chem. J., 23, 31 (1957). (in Russian).
5. Bell, R. P., and Gelles, E., J. Chem. Soc., 2734 (1951).