1. Critical loads Advisory Group (CLAG): 1995, Critical Loads of Acid Deposition for UK Freshwaters, Institute of Freshwater Ecology, Penicuik, pp 77.
2. Emmett, B.A., Reynolds, B., Stevens, P.A., Noms, D.A., Hughes, S., G�rres, J. & Lubrecht, I.: 1993, Ambio 22, 386.
3. Fuller, R.M., Groom, G.B. & Jones, A.R.: 1994, Photogram. Eng. Rem. Sens. 60, 553.
4. Grennfelt, P. & Hultberg, H.: 1986, Water, Air, and Soil Pallut. 30, 945?963.
5. Harriman, R., Gillespie, E., King, D., Watt, A.W., Christie, A.E.G., Cowan, A.A. & Edwards, T.: 1990, J. Hydrol. 116, 267.