1. Paul EA, Campbell CA, Rennie CA, McCallum KJ: Investigations of the dynamics of soil humus, utilizing carbon-dating techniques. Trans 8th Intern Congr Soil Sci. 1964, 3: 201-
2. Thorn KA, Folan DW, MacCarthy P: Characterization of the International Humic Substances Society Standard and Reference Fulvic and Humic Acids by Solution State Carbon-13 and Hydrogen-1 Nuclear Magnetic Resonance Spectrometry. Water Resources Investigations Report 89-4196, US Geological Survey, Denver, CO. 1989
3. Stevenson FJ: Humus Chemistry. 1994, John Wiley Sons, Inc., New York, 46-2
4. Steelink C: Elemental Characteristics of Humic Substances. Humic Substances in Soil, Sediment, and Water. Edited by: Aiken GR, McKnight DM, Wershaw RL, MacCarthy P. 1985, John Wiley, New York, 457-476.
5. Aquatic Humic Substances–Influence on Fate and Treatment of Pollutants. Edited by: Suffet IH, MacCarthy P. 1989, Advances in Chemistry Series 219, American Chemical Society, Washington, DC