1. Stewart, W. F. P., Nitrogen Fixation in Plants (Athlone Press, London, 1966).
2. Bond, G., in Recent Aspects of Nitrogen Metabolism in Plants, (edit. by Hewitt, E. J., and Cutting, C. V.), 15–25, (Academic Press, New York, 1968).
3. Phillips, D. A., Torrey, J. C., and Burris, R. H., Science, 174, 169–174 (1971).
4. Hardy, R. W. F., Holsten, R. D., Jackson, E. K., and Burns, R. C., Pl. Physiol., Lancaster, 43, 1185–1207 (1968).
5. Holsten, R. D., Burns, R. C., Hardy, R. W. F., and Hebert, R. R., Nature, 232, 173–176 (1971).