1. a Department of Policy Analysis (research group: Environmental Sociology) , National Environmental Research Institute , Frederiksborgvej 399, P.O. Box 358, DK-4000 , Roskilde , Denmark Phone: Fax: E-mail:
2. b Department of Agricultural Sciences , The Royal Veterinary and Agricultural University , Højbakkegaard Allé, DK-2630 , Taastrup , Denmark E-mail: