1. The use of sodium pyrophosphate for separating free humus substances and their organo-mineral compounds from soil;Aleksandrova;Pochvovednie,1960
2. Gel chromatography of humic acids;Swift;J. Soil Sci.,1971
3. Gel filtrarion of fulvic acid, a soil humic compound;Schnitzer,1968
4. The effects of chemical removal of silicate impurities on functional groups and physico-chemical characteristics of humic acids extracted with dilute NaOH and Na4P2O7 solutions;Piccolo,1985
5. Humic substances: chemistry and reactions;Schnitzer,1978