1. Clare Hall, University of Cambridge, Cambridge CB3 3AG, England
2. Department of City and Regional Planning, Harvard University, Cambridge, Massachusetts 02138, USA
3. Department of Geography, University of Newcastle, Newcastle, New South Wales 2308, Australia
4. Department of Geography, University of Sheffield, Sheffield S10 2TN, England
5. School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, England