1. Visiting scientist from the Forest Soils Laboratory, University of Alaska, Fairbanks, Alaska 99775, USA
2. Institute of Soil Science and Soil Geography, University of Bayreuth, P.O. Box 10 12 51, 8580 Bayreuth, FRG
3. Laboratory for Inorganic Chemistry, University of Bayreuth, P.O. Box 10 12 51, 8580 Bayreuth, FRG