http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Dissolved silica in the tidal Potomac River and Estuary, 1979-81 water years
a water quality study of the tidal Potomac River and Estuary
vii, 48 pages : illustrations, maps ; 28 cm.
Water-quality study of the tidal Potomac River and Estuary
U.S. Geological Survey water-supply paper ; 2234-H