1. Institute of Organic Chemistry with Centre of Phytochemistry; Bulgarian Academy of Sciences; Sofia 1113 Bulgaria
2. Centre for Environmental Sciences; Hasselt University; Agoralaan - building D B-3590 Diepenbeek Belgium
3. INRA, UMR BIOGECO INRA 1202; University of Bordeaux; 33405 Talence France
4. Phytotech Foundation; Umweltbeobachtung und Oekologische Planung Quartiergasse 12; 3013 Bern Switzerland