National water conditions [electronic resource] / U.S. Dept. of the Interior, Geological Survey [and] Canada Department of the Environment, Water Resources Branch.
Imprint
[Reston, Va.] : U.S. Dept. of the Interior, Geological Survey [and] Canada Department of the Environment, Water Resources Branch, [1982]-
Continued by online publication with same title, available via the Internet from http://h2o.usgs.gov/nwc/NWC/html/TOC.html (current issue available at http://h2o.usgs.gov/nwc/NWC/html/NWC.html ).
