1. Wickramasinghe, N. C., and Reddish, V. C., Nature, 218, 661 (1968).
2. Corruccini, R. J., in Pure and Applied Cryogenics, 5, 65 (Pergamon Press, 1966).
3. Dwyer, R. F., Cook, G. A., Shields, B. M., and Stellrecht, D. H., J. Chem. Phys., 42, 3809 (1965).
4. Sattar, A., thesis, Univ. Toronto (1965).
5. Hoyle, F., and Wickramasinghe, N. C., Mon. Not. Roy. Astro. Soc., 124, 417 (1962). Wickramasinghe, N. C., Interstellar Grains (Chapman and Hall, 1967).