Verbeek, J. (1999). The World Bank's unified survey projections: How accurate are theyn. World Bank.
Lua i Stíl Chicago (17ú heag.)Verbeek, Jos. The World Bank's Unified Survey Projections: How Accurate Are Theyn. Washington, D.C: World Bank, 1999.
Lua MLA (9ú heag.)Verbeek, Jos. The World Bank's Unified Survey Projections: How Accurate Are Theyn. World Bank, 1999.
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