(2021). World statistics pocketbook (2021 edition.). United Nations.
Chicago-Zitierstil (17. Ausg.)World Statistics Pocketbook. 2021 edition. New York: United Nations, 2021.
MLA-Zitierstil (8. Ausg.)World Statistics Pocketbook. 2021 edition. United Nations, 2021.
警告：这些引文格式不一定是100％准确.