Cita APA (7th ed.)

Worldwatch Institute, Gardner, G. T., Bright, C., & Starke, L. (1991). State of the world, 1991: A worldwatch institute report on progress toward a sustainable society (First edition.). W.W. Norton & Co..

Cita Chicago (17th ed.)

Worldwatch Institute, Gary T. Gardner, Chris Bright, i Linda Starke. State of the World, 1991: A Worldwatch Institute Report on Progress Toward a Sustainable Society. First edition. New York ; London: W.W. Norton & Co., 1991.

Cita MLA (8th ed.)

Worldwatch Institute, et al. State of the World, 1991: A Worldwatch Institute Report on Progress Toward a Sustainable Society. First edition. W.W. Norton & Co., 1991.