1. Schnitzer, M., Khan, S. U.: Humic Substances in the Environment. New York: Dekker 1972
2. Duchaufour, Ph., Jacquin, F.: Bull. A.F.E.S.1, 29 (1975)
3. Hayes, M. B. H., Swift, R. S., in: The Chemistry of Soil Constituents, p. 178 (Greenland, D. J., Hayes, M. H. B., eds.). Chichester: Wiley 1983
4. Hatcher, P. G., Spiker, E. C., in: Humic Substances and their Role in the Environment, p. 59 (Frimmel, F. H., Christman, R. F., eds.). Chichester: Wiley 1988; Thengh, B. K. G., Churchman, G. J., Newman, R. H.: Soil Sci.142, 262 (1986); Oades, J. M., Vassallo, A. M., Waters, A. G., Wilson, A.: Aust. J. Soil Res.25, 71 (1987); Catroux, G., Schnitzer, M.: Soil Sci. Soc. Am. J.51, 1200 (1987); Preston, C. M., Schnitzer, M.: ibid.53, 1422 (1989)
5. Preston, C. M., Axelson, D. E., Lévesque, M., Mathur, S. P., Dinel, H., Dudley, R. L.: Org. Geochem.14, 393 (1989)