Water-resources Activities of the U.S. Geological Survey in Pennsylvania, 1986-87 Robert E. Helm Published: 1987 Total Pages: 132 Get eBook
List of U.S. Geological Survey Geologic and Water-supply Reports and Maps for Pennsylvania and New Jersey Published: 1988 Total Pages: 248 Get eBook
New Publications of the Geological Survey Geological Survey (U.S.) Published: 1989 Total Pages: 836 Get eBook
New Publications of the U.S. Geological Survey Geological Survey (U.S.) Published: 1992 Total Pages: 436 Get eBook
