1. Waters, W. A., “The Chemistry of Free Radicals” (Oxf. Univ. Press, 1948).
2. Waters, W. A., see ref. 1, p. 147 and p. 149.
3. Hey, D. H., et al., Research, 4, 386 (1951).
4. Szwarc, M., J. Chem. Phys., 17, 431 (1949); Proc. Roy. Soc., A, 198, 267 (1949).
5. Ladacki, M., Leigh, C. H., and Szwarc, M., Proc. Roy. Soc. (in the press).