1. T. M. Addiscott, A. P. Whitmore, and D. S. Powlson, 1991 . Farming, Fertilisers and the Nitrate Problem . CAB International170 pp.
2. C. J. Barr, R. G. H. Bunce, R. T. Clarke, R. M. Fuller, M. T. Furse, M. K. Gillespie, G. B. Groom, C. J. Hallam, M. Hornung, D. C. Howard, and M. J. Ness, 1993 . Countryside Survey 1990. Main Report . London: Department of the Environment.174 pp.
3. N. D. Boatman, L. J. Rew, A. J. Theaker, and R. J. Froud-Williams, 1994 . The impact of nitrogen fertilisers on field margin flora . In:BCPC Monograph No. 58: Field Margins: Integrating Agriculture and Conservation.Thornton Heath, Surrey, UK: British Crop Protection Council, pp.209 -214 .
4. Effects of Nutrient Enrichment in Dutch Chalk Grassland