1. Agricultural Research Council Working Party (1980). The Nutritional Requirements of Ruminant Livestock, CAB, UK.
2. Abu Damir, H. (1980). MVSc Thesis, University of Khartoum, Sudan.
3. Mahmoud, O. M., Fatma, E., Amal, O. B. &Hassan, M. A. (1983).Journal of Comparative Pathology,93, 591–595.
4. Mills, C. F., Dalgarno, A. G., Williams, R. B. &Quarterman, J. (1967).British Journal of Nutrition,21, 751–768.
5. Nelson, D. R., Wolff, W. A., Blodgett, D. J., Luecke, B., Ely, R. W., &Zachary, J. F. (1984).Journal of the American Veterinary Medical Association,184, 1480–1485.