"Hydrology." . . "Hydrologie." . . . . . "Guide to obtaining USGS Information"@en . . . . . "Handbooks and manuals"@en . . . . "Guide to obtaining USGS information" . "Guide to obtaining USGS information"@en . "Guide to obtaining USGS information" . . . . . . . . . "Directories"@en . . . . . . . . . . . . . . . "Gidsen (vorm)" . . . . . . . "Wissenschaftliche Einrichtung." . . "Geological Survey U.S." . . . . "Adressbuch." . . "Geologie." . . "United States" . . "Aardwetenschappen." . . "Geology." . . "USA." . .