Worldwatch Institute. (2006). Vital signs 2006-2007: The trends that are shaping our future. Norton.
Chicago-viite (17. p.)Worldwatch Institute. Vital Signs 2006-2007: The Trends That Are Shaping Our Future. New York: Norton, 2006.
MLA-viite (9. p.)Worldwatch Institute. Vital Signs 2006-2007: The Trends That Are Shaping Our Future. Norton, 2006.
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