1. 1. Daniel, M. D. et al Science 223, 602–605 (1984). 2. Marx, P. A. et al. Science 223, 1083–1086 (1984). 3. Stromberg, K. et al. Science 224, 289–292 (1984). 4. Sonigo, P., Barker, C., Hunter, E. & Wain–Hobson, S. Cell 45, 375–385 (1986). 5. Power, M. D. et al. Science 231, 1567 (1986). 6. Daniel, M. D. et al. Science 228, 1201–1204 (1985). 7. Kanki, P. J., Alroy, J. & Essex, M. Science 230, 951–954 (1985). 8. Fultz, P. N. et al. Proc. natn. Acad. Sci. U.S.A. 83, 5286–5290 (1986). 9. Murphey–Corb, M. et al. Nature 321, 435–437 (1986). 10. Letvin, N. L. et al. Science 230, 71–73 (1985). 11. Kanki, P. S. et al. Lancet i, 1330–1332 (1985). 12. Guyader, M. et al. Nature 326, 662–669 (1987). 13. AHzon, M., Wain–Hobson, S., Montagnier, L. & Sonigo, P. Cell 46, 63–74 (1986). 14. Clavel, F. et al. Nature 324, 691–695 (1986). 15. Chalifoux, L. V. et al. Lab. Invest. 55, 43–50 (1986). 16. Sonigo, P. et al. Cell 42, 369–382 (1985). 17. Wain–Hobson, S., Sonigo, P., Danos, O., Cole, S. & Alizon, M. Cell 40, 9–17 (1985). 18. Hirsch, V. et al Proc. natn. Acad. Sci. U.S.A. 83, 9754–9758 (1986). 19. Kornfeld, H., Riedel, N., Viglianti, G. A., Hirsch, V. & Mullins, J. I. Nature 326, 610–613 (1987). 20. Desrosiers, R. C., Daniel, M. D., Letvin, N. L., King, N. W. & Hunt, R. D. Nature 327, 107 (1987). 21. Kanki, P. J. et al Science 228, 1199–1201 (1985). 22. .Kanki, P. J. et al Science 232, 238–843 (1986). 23. . Benveniste. R E. et al J. Virol 60, 483–490 (1986). 24. Perez, L. G., Davis, G. L. & Hunter, E. / Virol (in the press). 25. Davis, J. L., Molineaux, S. & Clements, J. E. / Virol 61, 1325–1331 (1987). 26. Brun–Vezinet, F. et al Lancet ii, 128–132 (1987). 27. Clavel, F. et al Science 233, 343–346 (1986). 28. Zarling, J. M. et al. Nature 323, 344–346 (1986). 29. Putney, S. D. et al Science 234, 1392–1395 (1986). 30. Lasky, L. et al Science 233, 209–212 (1986). 31. Wilbur, W. J. & Lipman, D. J. Proc. natn. Acad. Sci. U.S.A. 80, 726–730 (1983). 32. Kawakami, T. et al. Virology 156, 853–869 (1987). 33. Seiki, M., Hattori, S., Hiriyama, Y. & Yoshida, M. Proc. natn. Acad. Sci. U.S.A. 80,3618–3622(1983). 34. Schwartz, D. E., Tizard, R. & Gilbert, W. Cell 32, 853–869 (1983). 35. Nabel, G. & Baltimore, D. Nature 326, 711–713 (1987).