H. Weiss, M-A. Courty, W. Wetterstrom, F. Guichard, L. Senior, R. Meadow, and A. Curnow, “The Genesis and Collapse of Third Millennium North Mesopotamian Civilization,” Science (August 20, 1993), pp. 995–1004. See also the news reports by J. Wilford, “Collapse of Earliest Known Empire is Linked to Long, Harsh Drought,” New York Times (August 24, 1993), p. C-1, and C. Gorman, “Mystery of the 300-year Drought,” Time (August 30, 1993), p. 46.