APA (7th ed.) Citation

United Nations Population Fund. (1999). The State of world population 1999: 6billion : a time for choices. UNFPA.

Chicago Style (17th ed.) Citation

United Nations Population Fund. The State of World Population 1999: 6billion : A Time for Choices. New York: UNFPA, 1999.

MLA (8th ed.) Citation

United Nations Population Fund. The State of World Population 1999: 6billion : A Time for Choices. UNFPA, 1999.