1. Abelson, P.: 1983, Sci. 221, 115.
2. Abelson, P.: 1987, Sci. 238, 141.
3. Abrahamsen, G.,. Bjor, R., Horntvedt, R., and Tevite, B.: 1976, in F. Braekke (ed.), Impact of Acid Precipitation on Forests and Freshwater Ecosystems in Norway, SNSF-Project Norway FR 6/76:36.
4. Abrahamsen, G., Horndtvedt, R., and Tveite, B.: 1977, Water, Air, and Soil Pollut. 8, 57.
5. Bates, R.: 1959, Treatise on Analytical Chemistry, Vol. 1, Part 1, Interscience. New York pp. 361 ff.