1. Adams S, Titusa R, Pietersen K, Tredoux G, Harris C (2001) Hydrochemical characteristics of aquifers near Sutherland in the Western Karoo, South Africa. J Hydrol 241:91–103
2. Adelena SMA (2006) Nitrate pollution of groundwater in Nigeria. In: Xu Y, Usher BH (eds) Groundwater pollution in Africa, Taylor and Francis (Balkema), The Netherlands, pp 37–45
3. Ako AA, Nkeng GE, Takem GE (2008) Water quality and occurrence of water borne diseases in the Douala 4th district Cameroon. Water science and technology Ref No: WM 046 (Article in Press)
4. APHA/AWWA/WEF (1998) Standard methods for the examination of water and wastewater. American Public Health Association, American Water Works Association, Water Environment Federation Publication. 20th edn. American Public Health Association, Washington DC, USA p 1220
5. Appello CAJ, Postma D (1993) Geochemistry Groundwater and Pollution. A A Balkema, Rotterdam, p 534