1. Department of Water Affairs and Forestry (1996). Water quality guidelines, domestic use, vol. 1 (2nd ed.). Pretoria: DWAF.
2. DeZuane, P. E. J. (1977). Chemical parameters—inorganics. In Handbook of drinking water quality (pp. 49–65). NY: Van Nostrand Reinhold.
3. EPA (1983). EPA methods of chemical analysis of water and wastewater. EPA/600/4-79/020. USA, 374.3.1–375.4.3.
4. Fatoki, O. S., Lujiza, N., & Ogunfowokon, A. O. (2002). Trace metal pollution in Umtata River. Water SA, Vol. 28, No. 2. (pp. 183–189). Pretoria.
5. Friberg, L., Elinder, C. G., Kjellstroem, T., & Nordberg, G. F. (Eds.). (1986). Cadmium and health: A toxicological and epidemiological appraisal. Vol. 11, Effects and response. Boca Raton, FL: CRC Press.