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2. Gregory, H., Hardy, P. M., Jones, D. S., Kenner, G. W., and Sheppard, R. C., Nature, 204, 931 (1964).
3. Beacham, J., Bentley, P. H., Gregory, R. A., Kenner, G. W., MacLeod, J. K., and Sheppard, R. C. (see following article).
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5. Smith, E. L., Fed. Proc. (in the press); quoted by Jukes, T. H., Biochem. Biophys. Res. Comm., 19, 391 (1965).