Conference on Regional Economic Development Bellagio, Italy, Organization for European Economic Cooperation. European Productivy Agency, Isard, W., & Cumberland, J. H. (1961). Regional economic planning: Techniques of analysis for less developed areas : papers and proceedings of the first study conference on problems of economic development organised by the European Pruductivity Agency ... European Productivity Agency of the Organisation for European Economic Co-operation.

Conference on Regional Economic Development Bellagio, Italy, Organization for European Economic Cooperation. European Productivy Agency, Walter Isard, và John H. Cumberland. Regional Economic Planning: Techniques of Analysis for Less Developed Areas : Papers and Proceedings of the First Study Conference on Problems of Economic Development Organised by the European Pruductivity Agency ... Paris: European Productivity Agency of the Organisation for European Economic Co-operation, 1961.

Conference on Regional Economic Development Bellagio, Italy, et al. Regional Economic Planning: Techniques of Analysis for Less Developed Areas : Papers and Proceedings of the First Study Conference on Problems of Economic Development Organised by the European Pruductivity Agency ... European Productivity Agency of the Organisation for European Economic Co-operation, 1961.