1. Alexsandrova LN (1960) The use or pyrophosphate for isolating free humic substances and their organic-mineral compounds from the soil. Soviet Soil Sci., 190-197
2. Aomine S and Jackson ML (1959) Allophane determination in ando soils by cation exchange delta value. Soil Sci. Soc. Am. Proc., 23, 210-214
3. Atkinson RR, Posner AM and Quirk J (1968) Crystal nucleation in Fe (III) solutions and hydroxyde gels. J. Inorg. Nucl. Chem., 30, 2371-2381
4. Avery BW and Bascomb CL (1982) Soil Survey Laboratory Methods., Soil Survey of England-Wales (Harpenden), 6
5. Baize D(1988) Guide Des Analyses Courantes En Pédologie: Choix-Expression - Présentation - Interprétation., INRA, 172 pages