1. Base of principal aquifer for parts of the North Platte, South Platte, and Twin Platte Natural Resources District, western Nebraska Author/Creator: Hobza, Christopher M., cartographer Publication/Creation: [Reston, Va.] : U.S. Department of the Interior, U.S. Geological Survey, 2014 Format: Map Access & Availability: Loading
2. Bedrock-surface altitude in the midwestern basins and arches region of Indiana, Ohio, Michigan, and Illinois Author/Creator: Geological Survey (U.S.), cartographer Publication/Creation: Columbus, Ohio : U.S. Department of the Interior, U.S. Geological Survey, 1993 Format: Map Access & Availability: Loading