1. Organic matter by Walkley-Black method;Allison,1965
2. Soil science and the search for unifying concepts;Arnold;Journal of Soil Science,1977
3. Le Littoral du Mont Cameroun, Etude Géomorphologique;Battistini,1983
4. Montmorillonite and other smectite minerals;Borchardt,1977
5. Red soils in Indonesia;Buurman,1980