1. Abdin, G., - 1948 - Physical and Chemical Investigations relating to algal growth in the River Nile; Bull. Inst. Egypte, 29: 19?44.
2. Acocks, J. P. H., - 1953 - Veld Types of South Africa; Union of South Africa, Department of Agriculture. Division of Botany, Botanical Survey Memoir, No. 28.
3. Allen, K. R., - 1951 - The Horokiwi Stream ? A Study of a Trout Population; New Zeal. Mar. Dep. Fish. Bull., No. 10.
4. American Public Health Association: Standard Methods for the Examination of Water and Sewage, 10th edition, 1955.
5. Barnard, K. H., - 1950 - Descriptive Catalogue of South African Decapod Crustacea; Ann. S. Afr. Mus. 38: 1?658.