1. Dirac, P. Proc. R. Soc. A126, 360???365 (1930). 2. Dirac, P. Proc. R. Soc. A133, 60???72 (1931). 3. Anderson, C. D. Phys. Rev. 43, 491???494 (1933). 4. Chamberlain, O., Segre, E., Wiegand, C. & Ypsilantis, T. Phys. Rev. 100, 947???950 (1955). 5. Cork, B., Lambertson, G. R., Piccioni, O. & Wenzel, W. A. Phys. Rev. 104,1193???1197 (1956). 6. Dorfan, D. E., Eades, J., Lederman, L. M., Lee, W. & Ting, C. C., Phys. Rev. Lett. 14, 1003???1006 (1965). 7. Antipov, Yu. M. et al. NucL Phys. B31, 235???252 (1971). 8. Morrison, P. Am. J. Phys. 26, 358???368 (1958). 9. Beverini, N. et al. A Measurement of the Gravitational Acceleration of the Antiproton CERN Experiment PS200, January 1986 (CERN, Geneva, 1986). 10. Goldman, T, Hughes, R. J. & Nieto, M. N. Phys. Lett. 171B, 217???222 (1986). 11. Rafelski, J. Phys. Lett. 91B, 281???284 (1980). 12. Strottman, D. Phys. Lett. 119B, 39???42 (1982). 13. Cahay, M., Cugnon, J., Jasselette, P. & Vandermeulen, J. Phys. Lett. 115B, 7???10 (1982). 14. Clover, M. R., DeVries, R. M., DiGiacomo, N. J. & Yariv, Y. Phys. Rev. C26, 2138???2151 (1982). 15. Cugnon, J. & Vandermeulen, J. Phys. Lett. 146B, 16???20 (1984). 16. McGaughey, P. L., Clover, M. R. & DiGiacomo, N. J. Phys. Lett. 166B, 264???266 (1986). I7 Bocquet, J. P. et al. Phys. Lett. 182B, 146???150 (1986). 18. Billinge, R. et al. in Physics with Antiprotons at LEAR in the ACOL Era (eds Gastaldi, et al.) (Frontieres, Gif???Sur???Yvette, France, 1985). 19. Garetta, D. et al. in Physics with Antiprotons at LEAR in the ACOL Era (eds Gastaldi, U., et al.) (Frontieres, Gif???sur???Yvette, France, 1985). 20. Garetta, D. et al. Phys. Lett. 135B, 266???270 (1984); 139B, 464 (1984). 21. Friedman, E. & Lichtenstadt, J. Nud. Phys. A455, 573???583 (1986). 22. Wong, C.???Y., Kerman, A. K., Satchler, G. R. & MacKellar, A. D., Phys. Rev. C29, 574???580 (1984). 23. Auerbach, E. H., Dover, C. B. & Kahana, S. Phys. Rev. Lett. 46, 702???705 (1981). 24. Kahana, S. H. & Sainio, M. E. Phys. Lett. 139B, 231???234 (1984). 25. Kanert, W. thesis, Technische Univ., Miinchen (1986). 26. Bacher, R. et al. Annual Report on Nuclear Physics Activities 104???105 (KfK 4159 Kernfor??? schungszentrum Karlsruhe, 1986). 27. Dover, C. B. NucL Phys. A416, 313c???334c (1984). 28. Batty, C. I. NucL Phys. A372, 418???432 and 433???444 (1981). 29. Poth, H. et al. in Physics with Antiprotons at LEAR in the ACOL Era (eds Gastaldi, U. et al 581???591. (Frontieres, Gif???sur???Yvette, France, 1985); Phys. Lett. B176,327???333 (1986);
2. Z. Phys. A325, 261???265 (1986). 30. Kanert, W. Phys. Rev. Lett. 56, 2368???2371 (1986). 31. Daniel H. et al. Z. Phys. A326, 523???525 (1987). 32. Kaufmann, W. B. & Pilkuhn, H. Phys. Lett. 166B, 279???281 (1986). 33. Leon, M. NucL Phys. A260, 461???473 (1976). 34. Batty, C. J. Nature 323, 487 (1986). 35. Balestra, F. et al NucL Phys. A465, 714???732 (1987). 36. Iljinov, A. S., Nazaruk, V. I. & Chigrinov, S. E. NucL Phys. A382, 378???400 (1982). 37. Bugg, W. M., Condo, G. T, Hart, E. L., Cohn, H. O. & McCulloch, R. D. Phys. Rev. Lett. 31, 475???478 (1973). 38. Armenteros, R. & French B, in Antinucleon??? Nucleon Interactions in High???Energy Physics Vol. IV (ed. Burhop, E. H. S.) 237 (Academic, New York, 1969). 39. Baltay, C. et al. Phys. Rev. 145, 1103???1111 (1966). 40. Orfanidis, S. J. & Rittenberg, V. Nud. Phys. B59, 570???582 (1973). 41. Cugnon, J. & Vandermeulen, J. NucL Phys. A445, 717???756 (1985). 42. Ekspong, A. G., Frisk, A, Nilsson, S. & Ronne, B. E. NucL Phys. 22, 353???409 (1961). 43. Batusov, Yu. A. Europhys. Lett. 2, 115???122 (1986). 44. Balestra et al NucL Instrum. Meth. A234, 30???41 (1985). 45. Sunier, J. W. NucL Instrum. Meth. A241, 139???152 (1985). 46. Daniel, H. et al. Verhandl DPG (VI) 22, IV, E???8.3 (1987). 47. Balestra, F. et al NucL Phys. A452, 573???590 (1986). 48. Burgov, N. A. et al Soviet J. NucL Phys. 24, 620???622 (1976). 49. Amann, J. F. et al Phys. Rev. Lett. 35, 1066???1069 (1975). 50. Kaufman, S. B. et al Phys. Rev. C32, 1977???1985 (1985). 51. Jackson, H. E. et al Phys. Rev. C18, 2656???2665 (1978). 52. Gumming, J. B., Haustein, P. E., Stoenner, R. W., Mausner, L. & Naumann, R. A. Phys. Rev. CIO, 739???755 (1974). 53. Moser, E. F. et al Phys. Lett. B179, 25???29 (1986). 54. Moser, E. F. thesis, Technische Univ., Munchen (1987). 55. Daniel, H. et al Verhandl DPG (VI) 22, IV, C???2.6 (1987). 56. Maddox, J. Nature 324, 299 (1986).