Centre for Development and Environment,University of Berne,Hallerstrasse 12,3012 Bern,Switzerland E-mail:liniger@giub.unibe.ch;
P.O.Box 14893,Nairobi,Kenya,E-mail:dbtrat@yahoo.com;
International Cooperation Centre,Vrije Universiteit Amsterdam,De Boelelaan 1105,1081 HV Amsterdam,The Netherlands,E-mail:WRS.Critchley@dienst.vu.nl;
2 Madang Avenue,Box Hill North,Victoria 3129,Australia,E-mail:dennisc@warrandyte.starway.net.au;
International Soil Reference and Information Centre,P.O.Box 353-6700 A J Wageningen-The Netherlands E-mail:vanlynden@isric.nl;
Centre for Development and Environment,University of Berne,Hallerstrasse12,3012 Bern,Switzerland E-mail:gudrun@giub.unibe.ch;
