1. Institute of Economics and Economic Development, Faculty of Economics and Business Administration, University of Szeged, Szeged, Hungary; and Agglomeration and Social Networks Lendület Research Group, Centre for Economic and Regional Studies, Hungarian Academy of Sciences, Budapest, Hungary.
2. Department of Human Geography and Planning, Utrecht University, Utrecht, the Netherlands; Stavanger Centre for Innovation Research, UiS Business School, Stavanger University, Stavanger, Norway.
3. Agglomeration and Social Networks Lendület Research Group, Centre for Economic and Regional Studies, Hungarian Academy of Sciences, Budapest, Hungary; and International Business School Budapest, Budapest, Hungary.