1. Manual SPREAD: prediction of nitrate, hardness, chloride and sulphate in shallow groundwater (in Dutch) Kiwa Onderzoek and Advies, Nieuwegein, The Netherlands;Beekman;Report nr. SWE 98.012,1998
2. Deposition of acidifying components in The Netherlands during 1980–1995. Report National institute of public health and environment;Bleeker,1996
3. The quality of the upper groundwater;Boumans,1995
4. Broers, H.P., (2002) Strategies for regional groundwater quality monitoring. Netherlands Geographical Studies no. 306. PhD Thesis Universiteit Utrecht, p. 231.
5. Broers, H.P., (2004) The spatial distribution of groundwater age for different geohydrological situations in the Netherlands: implications for groundwater quality monitoring at the regional scale. Journal of Hydrology, in press.