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2. Commission of the European Communities, International Monetary Fund, Organisation for Economic Cooperation and Development, United Nations and World Bank 1993 System of National Accounts 1993
3. Cooper , R. 2014 Will China's Economy Surpass the US in 2014? Century Weekly http://scholar.harvard.edu/files/cooper/files/century5.14chinagdp.pdf
4. Deaton , A. B. Aten 2014 Trying to Understand the PPPs in ICP 2011: Why Are the Results so Different?