1. K. SVOBODA, D. J. SILVESTER, Int. J. Appl. Radiation Isotopes, 23 (1972) 203. Letter to the editors by E. LEBOWITZ.
2. L. J. LANZEROTTI, R. C. REEDY, J. R. ARNOLD, Science, 179 (1973) 1232.
3. E. A. SCHWEIKERT, J. R. McGINLEY, J. J. STOCK, Trans. Am. Nucl. Soc. International Nuclear and Atomic Activation Analysis Conference and Nineteenth Annual Meeting on Analytical Chemistry in Nuclear Technology, October 14–16, Gatlinburg, Tenessee, 1975.
4. A. BUDZANOWSKI, G. BAUR, C. ALDERLISTEN, J. BOJOWALD, C. MAYER-BORICKE, W. OELERT, P. TUREK, F. RÖSEL, D. TRAUTMANN, Phys. Rev. Lett., 41 (1978) 635.
5. J. R. WU, C. C. CHANG, H. D. HOLMGREN, Phys. Rev. Lett., 40 (1978) 1013.