Brown, L. R., Flavin, C., Renner, M., & Starke, L. (1999). Vital signs 1999: The environmental trends that are shaping our future. W.W. Norton.
Cita Chicago (17th ed.)Brown, Lester Russell, Christopher Flavin, Michael Renner, i Linda Starke. Vital Signs 1999: The Environmental Trends That Are Shaping Our Future. New York: W.W. Norton, 1999.
Cita MLA (8th ed.)Brown, Lester Russell, et al. Vital Signs 1999: The Environmental Trends That Are Shaping Our Future. W.W. Norton, 1999.
Atenció: Aquestes cites poden no estar 100% correctes.