http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Preliminary map showing the potentiometric surface of the Aquia aquifer in southern Maryland, September 1984
by Frederick K. Mack, Judith C. Wheeler, Stephen E. Curtin, and David C. Andreasen.
Relief shown by contours and spot heights.
"Prepared in cooperation with Maryland Geological Survey and Maryland Energy Administration."
Water-resources investigations report ; 85-4338