1. 6. U.S. Department of Agriculture. 1986. Extension Committee on Organization and Policy. Groundwater education: A challenge to the cooperative extension system.
2. 5. U.S. Department of Agriculture. 12, 1985. Experiment Station Committee on Organization and Policy. Groundwater quality and management: Research and extension.
3. 7. U.S. Environmental Protection Agency. 12, 1986. National survey of pesticides in drinking water wells. Ground-Water Protection Update, pp. 4–5.
4. 3. Porter Keith S. Winter-Spring 1986. The groundwater pollution learning curve: A long climb. Environmental Update. Cornell University Center for Environmental Research, p. 5.