1. Department of Civil Engineering, University of Coimbra and INESC, 3000 Coimbra, Portugal
2. Fisher College of Business, Ohio State University, Columbus, Ohio 43210-1399
3. University of Coimbra and INESC, 3000 Coimbra, Portugal
4. Center for Technology, Environment and Development, Clark University, 950 Main Street, Worcester, Mass. 01610-1477