1. National Agency of Environmental Protection, Air Pollution Laboratory, Rise National Laboratory, DK-4000 Roskilde, Denmark
2. Present affiliation: Physics Department, Risn National Laboratory, DK-4000 Roskilde, Denmark.
3. Physics Department, Risr National Laboratory, DK-4000 Roskilde, Denmark
4. Present filiation: Danish Meteorological Institute, DK-2100 Copenhagen O, Denmark.