1. J. A. Simpson, Ann. Rev. Nucl. and Part. Sci.33, 323 (1983).
2. M. Boezioet al., Astrophys. J.518, 457 (1999).
3. R. Bellottiet al., Phys. Rev.D60, 052002 (1999).
4. AMS Collaboration, Phys. Lett. B (to be published, 1999).
5. T. Sanukiet al., inProc. 26th Int. Cosmic Ray Conf., Salt Lake City, 3, 93 (1999).