(2021). World statistics pocketbook (2021 edition.). United Nations.
Cita Chicago (17th ed.)World Statistics Pocketbook. 2021 edition. New York: United Nations, 2021.
Cita MLA (8th ed.)World Statistics Pocketbook. 2021 edition. United Nations, 2021.
Atenció: Aquestes cites poden no estar 100% correctes.