Não informado. (1981). Balance of Payments Statistics Yearbook. International Monetary Fund.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Balance of Payments Statistics Yearbook. Washington: International Monetary Fund, 1981.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Balance of Payments Statistics Yearbook. International Monetary Fund, 1981.
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