United Nations Population Fund. (1999). The State of world population 1999: 6billion : a time for choices. UNFPA.
Chicagoスタイル(17版)引用形式United Nations Population Fund. The State of World Population 1999: 6billion : A Time for Choices. New York: UNFPA, 1999.
MLA(8版)引用形式United Nations Population Fund. The State of World Population 1999: 6billion : A Time for Choices. UNFPA, 1999.
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