1. House of Lords Select Committee on European Communities. “16th Report: Organic Farming and the European Union” (HMSO, London, 1999).
2. MacKerron, D. K. I. et al. http://www.scri.sari.ac.uk/document/AnnReps/AnRp989.pdf (pp. 60–72).
3. Warne, J. Farmers Weekly 130, No. 12, 91–92 (1999).
4. Tschape, H. et al. Epidemiol. Infect. 114, 441–450 (1995).
5. Nolte, C. & Werner, W. Biol. Agric. Horticult. 10, 235–254 (1994).