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2. Human capital, natural resources and the purchasing power parity doctrine: some empirical results;Clague;Economia Internazionale,1972
3. United Nations International Comparison Project: Phase II; International Comparisons of Real Product and Purchasing Power;Kravis,1978
4. Real GDP per capita for more than one hundred countries;Kravis;Economic Journal,1978
5. Problems in comparing present growth rates for developed and less developed countries;Kuznets;Economic Development and Cultural Change,1972