1. Watt, W., and Johnson, W., Nature, 215, 384 (1967).
2. Brydges, W. T., Badami, D. V., Joiner, J. C., and Jones, G. A., Polymer Preprints Amer. Chem. Soc., 9, 1310 (1968).
3. Otani, S., Carbon, 3, 31 (1965).
4. Bacon, R., and Schalamon, W. A., Paper MI 58, Eighth Biennial Conf. on Carbon, Buffalo (NY) (1967).
5. Johnson, J. W., Marjoram, J. R., and Rose, P. G., Nature, 221, 358 (1969).