Description
Item Description:Title from PDF title screen (viewed May 8, 2009).
Electronic resource.
Physical Description:iv, 11 pages : digital, PDF file.
Format:Mode of access: Internet from the USGS web site. Address as of 5/8/09: http://pubs.usgs.gov/of/2009/1058/pdf/OF2009-1058.pdf ; current access available via PURL.
Bibliography:Includes bibliographical references (page 11).