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2. Zeuner, F. E., A History of Domesticated Animals, 183 (Hutchinson, London, 1963).
3. Ryder, M. L., in The Domestication and Exploitation of Plants and Animals (edit. by Ucko, P. J., and Dimbleby, G. W.) (Duckworth, London, 1969).
4. Ryder, M. L., Austral. J. Sci., 25, 499 (1963).
5. Ryder, M. L., Nature, 204, 555 (1964).