1. Cairns, J., Nature255 (1975) 197.
2. Potten, C. S., Hume, W. J., Reid, P., and Cairns, J., Cell15 (1978) 899.
3. Hume, W. J., in: Stem cells: their identification and characterisation, p. 233. Ed. C. S. Potten, Churchill Livingstone, Edinburgh 1983, in press.
4. Potten, C. S., UCLA Symposia. Alan Liss Inc., New York 1983, in press.
5. Potten, C. S., in: Stem cells: their identification and characterisation, p. 155. Ed. C. S. Potten. Churchill Livingstone, Edinburgh 1980.