1. The difference between the potentiometric surfaces of the Aquia Aquifer, September 1982 and September 1997 in Southern Maryland [microform] Yale Public content 1999. 2008-08-07T13:21:13Z. 2008-08-07T13:21:13Z. Curtin, Stephen E. U.S. Geological Survey ; Branch of Information Services [distributor. English. Public. Maryland, Southern and Aquia Formation.