1. Adams, F. C., M. J. van Craen, and P. J. van Espen. 1980. Environ Sci Technol 14: 1002–1005.
2. Barrie, L. A., R. H. Hoff, and S. M. Daggupaty. 1981. Atmos Environ 15: 1407–1419.
3. Braun, H., H. Vogg, G. Halbritter, K.-R. Bräutigam, and H. Katzer. 1984. Recycling International 1: 1–2.
4. Brumsack, H., and H. Heinrichs. 1984. Environ Technol Lett 5: 7–22.
5. Cawse, P. A. 1980. Inorganic Pollution and Agriculture (Ministry of Agriculture, Fisheries and Food, London ) 326.