(2001). Levels and trends of contraceptive use as assessed in 1998. United Nations.
芝加哥风格引文Levels and Trends of Contraceptive Use as Assessed in 1998. New York: United Nations, 2001.
MLA引文Levels and Trends of Contraceptive Use as Assessed in 1998. United Nations, 2001.
警告：这些引文格式不一定是100％准确.