1. Dep. of Crop Production EcologySwedish Univ. of Agricultural SciencesBox 7043750 07UppsalaSweden
2. Dep. of Energy and TechnologySwedish Univ. of Agricultural SciencesBox 7032750 07UppsalaSweden
3. Biostatistics UnitInstitute of Crop Science, Univ. of Hohenheim70599StuttgartGermany