1. Adams, C. E., USNRDL-TR-209, 1958.
2. Sisefsky, J., Nature, 182, 1437 (1958).
3. Sisefsky, J., Brit. J. App. Phys. (in the press).
4. Sisefsky, J., Report Res. Inst. Nat. Def. (in preparation).
5. May, R., and Schneider, H., Atomkernenergie, 4, 28 (1959).