1. Hagen, A. & Langeland, A. Envir. Pollut. 5, 45–57 (1973).
2. Leivestad, H., Hendry, G., Muniz, I. P. & Snekvik, Y. in Impact of Precipitation on Forest and Freshwater Ecosystems in Norway (ed. Broekke, F. H.) 86–111 Res. Rep. 6/76, (SNSF-Project, Aas, 1976).
3. Leivestad, H. & Muniz, I. P. Nature 259, 391–392 (1976).
4. Glen, J. W., Homer, D. R. & Paren, J. G. in Isotopes and Impurities in Snow and Ice Symp., 263–268 (IAHS-AISH publ. 118, International Association for Hydrological Science, 1977).
5. Data 1979, 1980 from Norwegian Monitoring Programme for Long Range Transported Pollutants in Air and Precipitation (Norwegian Institute for Air Research, Lillestrøm).