1. Constance , Douglas H. J. Sanford Rikoon 1992 Agricultural Pesticide and Ground Water Issues: Research on Farmers in Missouri Regions Most Susceptible to Ground Water Contamination from Pesticide Use
2. Constance Douglas , H. J. Sanford Rikoon Yongmin Sun 1996 Pesticide use and water quality issues: a comparison of Missouri urbanites, farmers, and landlords