1. Bacon, R., and Tang, M. M., Carbon, 2, 221 (1964).
2. Johnson, W., and Watt, W., Nature, 215, 384 (1967).
3. Badami, D. V., Joiner, J. C., and Jones, G. A., Nature, 215, 387 (1967).
4. Johnson, D. J., and Tyson, C. N., Brit. J. Appl. Phys., 2, 787 (1969).
5. Bacon, R., and Schalamon, W. A., Applied Polymer Symposia, 9, 285–292 (1969).