Title from title screen (viewed on Sept. 08, 2008).
"April 1999."
Mode of access: Internet from the GPO permanent archive. Address as of 9/08/08: http://permanent.access.gpo.gov/waterusgsgov/water.usgs.gov/pubs/fs/FS-011-99/pdf/fs-011-99.pdf; current access is available via PURL.