Description
Item Description:Title from PDF title screen (viewed May 5, 2009).
Electronic resource.
Physical Description:iii, 6 pages : digital, PDF file.
Format:Mode of access: Internet from the USGS web site. Address as of 5/5/09: http://pubs.usgs.gov/ds/419/DS419.pdf ; current access available via PURL.
Bibliography:Includes bibliographical references (pages 3-4).