1. Soil organic matter in relation to altitude in equatorial Colombia;Alexander;Turrialba,1979
2. Mineral occurrence in soil environments;Allen,1989
3. Estimating relative ages from iron-oxide/total-iron ratios of soils in the western Po Valley, Italy;Arduino;Geoderma,1984
4. Nature and geography of South American soils;Beek,1968
5. Soils and Geomorphology;Birkeland,1984