1. Hughes, R. C., and Mautner, V., in Membrane Mediated Information, 1 (edit. by Kent, P. W.), 104–125 (MTP Press, Lancaster, 1973).
2. Baum, S. G., and Fox, R. I., Cold Spring Harb. Symp. quant. Biol., 39, 567–578 (1974).
3. Doerfler, W., Virology, 38, 587–606 (1969).
4. Temin, H., Adv. Cancer Res., 19, 74–77 (1974).
5. Khoury, G., Byrne, J. C., and Martin, M. A., Proc. natn. Acad. Sci. U.S.A., 69, 1925–1928 (1972).