1. ‘Humus Chemistry. Genesis, Composition, Reactions’;Stevenson,1994
2. ‘Humic Substances in the Global Environment and Implications on Human Health’;Piccolo,1994
3. ‘Humic Substances, Peats and Sludges. Health and Environmental Aspects’;Hayes,1997
4. ‘Humic Substances in Terrestrial Ecosystems’;Piccolo,1996
5. ‘Environmental Systems, An Introductory Text’;White,1992