1. Department of Urban Development and Mobility, Luxembourg Institute of Socio-Economic Research (LISER), 3 avenue de la Fonte, L-4364 Esch-sur-Alzette, Luxembourg; School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, England
2. Department of Border Region Studies, University of Southern Denmark, DK-6400 Sønderborg, Denmark