1. Paul Scherrer Institut; Villigen Switzerland
2. Chemical Laboratory V, Department of Chemistry; University of Copenhagen; Copenhagen Denmark
3. Remote Sensing Laboratories, Department of Geography; University of Zürich; Zürich Switzerland
4. Institute for Tropospheric Research; Leipzig Germany
5. Battelle, Pacific Northwest Laboratories; Richland Washington USA
6. North Rhine-Westphalia State Environment Agency; Essen Germany