8N., Limao and A., Venables, (1999) Infrastructure, Geographical Disadvantage and Transport Costs, Policy Research Working Paper. Washington DC: World Bank.
9R., Stem, (2002) "Quantifying Barriers to Trade in Services," Discussion Paper of Research Seminar in International Economics.
10B., Hoekman,, A., Matoo and P., English, [ed.]., (2002) Development, Trade and the WTO. Washington, DC.: World Bank.