1. Sommerville, J. Int. Rev. Biochem. 15, 79–156 (1977).
2. Macgregor, H. C. & Andrews, C. Chromosoma 63, 109–126 (1977).
3. Davidson, E. H. Gene Activity in Early Development (Academic, New York, 1976).
4. Appels, R. & Peacock, W. J. Int. Rev. Cytol. Suppl. 8, 69–126 (1978).
5. Bostock, C. J. & Sumner, A. T. The Eukaryotic Chromosome (North Holland, Amsterdam, 1978).