APA

Brown L. R., Worldwatch Institute, . (1991). State of the world, 1991: a Worldwatch Institute report on progress toward a sustainable society. New York: Norton.

Chicago

Brown Lester Russell, Worldwatch Institute, . 1991. State of the world, 1991: a Worldwatch Institute report on progress toward a sustainable society. New York: Norton.

Harvard

Brown L. R., Worldwatch Institute, . (1991). State of the world, 1991: a Worldwatch Institute report on progress toward a sustainable society. New York: Norton.

MLA

Brown Lester Russell, Worldwatch Institute, . State of the world, 1991: a Worldwatch Institute report on progress toward a sustainable society. New York: Norton. 1991.