1. Isolation and concentration techniques for aquatic humic substances;Aiken,1985
2. Chemical character and origin of organic acids in streams and seepage lakes of central Maine;David;Biogeochemistry,1991
3. Organic acidity in Maine (U.S.A.) lakes and in HUMEX Lake Skjervatjern (Norway);David;Finnish Humus News,1991
4. Characterization of organic acids in freshwater: A current status and limitations;Frimmel,1990
5. Compositional indicators of organic acid sources and reactions in natural environments;Hedges,1990