Cita APA (7th ed.)
Worldwatch Institute. (2014). Vital signs. Island Press.
Cita Chicago (17th ed.)
Worldwatch Institute. Vital Signs. Washington, District of Columbia: Island Press, 2014.
Cita MLA (9th ed.)
Worldwatch Institute. Vital Signs. Island Press, 2014.
Atenció: Aquestes cites poden no estar 100% correctes.