1. Clayson, D. B., Ann. Rep. Brit. Emp. Cancer Campaign, 29, 148 (1951); Brit. J. Cancer, 7, 460 (1953).
2. Walpole, A. L., Williams, M. H. C., and Roberts, D. C., Brit. J. Indust. Med., 11, 105 (1954).
3. Boyland, E., and Sims, P., J. Chem. Soc., 980 (1954).