Não informado. (2019). Statistical Yearbook. United Nations, Department of International Economic.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Statistical Yearbook. New York: United Nations, Department of International Economic, 2019.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Statistical Yearbook. United Nations, Department of International Economic, 2019.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.