1. Stewart, W. D. P. & Rosswall, T. The Nitrogen Cycle (The Royal Society, London, 1982).
2. Cooke, G. W. Phil. Trans. R. Soc. B281, 231–241 (1977).
3. Magee, P. N. Ambio 6, 123–125 (1977).
4. Frazer, P. & Chilvers, C. Sci. Total Envir. 18, 103–116 (1981).
5. The Nitrogen Cycle of the United Kingdom, A Study Group Report (The Royal Society, London, 1983).