-45 -- David Hummels (2007), 'Transportation Costs and International Trade in the Second Era of Globalization', Journal of Economic …, 64 (4), 685-703 -- Kenneth John Button and Henry Vega (2008), 'The Effects of Air Transportation on the Movement of Labor … Research and Policy Challenge', Transportation Planning and Technology, 26 (1), February, 1-8 -- A.A.J. Nederveen, J.W. Konings …