1. Kononova, M. M.: Soil Organic Matter, Its Nature, Its Role in Soil Formation and Soil Fertility. Oxford: Pergamon 1966
2. Hayes, M. H. B., MacCarthy, P., Malcolm, R. L., Swift, R., in: [4], p. 4
3. Schulten, H. R., Plage, B., Schnitzer, M.: Naturwissenschaften78, 311 (1991); Schulten, H. R., Schnitzer, M.: ibid.80, 29 (1993)
4. Hayes, M. H. B., MacCarthy, P., Malcolm, R. L., Swift, R. S.: Humic Substances II - In Search of Structure. Chichester: Wiley 1989
5. Osterberg, R., Mortensen, K.: Eur. Biophys. J.21, 163 (1992)