1. Dep. of Soil Management; Ghent Univ.; Coupure links 653 (B) 9000 Gent Belgium
2. Dep. of Natural Resources Management; Univ. of Kinshasa; 11850 Kinshasa Democratic Republic of the Congo
3. Dep. of Soil, Water and Environment Bioforsk; Fr. A. Dahlsvei 20 NO-1430 Ås Norway
4. Dep. of Geology and Soil Science; Ghent Univ.; Krijgslaan 281 (S8) 9000 Gent Belgium