1. Sunderland, N., in Plant Tissue and Cell Culture (edit. by Street, H. E.), chap. 7 (Blackwell, Oxford, 1973).
2. Harris, M., Cell Culture and Somatic Variation (Holt, Rinehart and Winston, New York and London, 1964).
3. Torrey, J. G., Proc. int. Conf. Plant Tissue Cult. (edit. by Grove, P. R., and White, A. R.), 473 (McCutchain, Berkeley, 1965).
4. Kao, K. N., Miller, R. A., Gamborg, O. L., and Harvey, B. L., Can. J. Genet. Cytol., 12, 297 (1970).
5. Luykx, P., Int. Rev. Cytol. Suppl II (1970).