1. I am indebted to R. M. Drisko for this remark.
2. For example, see N. Hashimoto and M. Kawai, Prog. Theor. Phys. 59, 1245 (1978).
3. For example, see D. H. Feng, T. Udagawa and T. Tamura, Nucl. Phys. A274, 262 (1976).
4. For example, see R. Bass, Nuclear Reactions with Heavy Ions, Springer-Verlag, Berlin, 1980.
5. M. A. Nagarajan, M. R. Strayer and M. F. Werby, Phys. Lett. 68B, 421 (1977).