A USGS zonal table for the Upper Cretaceous middle Cenomanian-Maastrichtian of the Western Interior of the United States based on ammonites, inoceramids, and radiometric ages [electronic resource] / by William A. Cobban ... [et al.].
Mode of access: Internet from the USGS web site. Address as of 9/25/07: http://pubs.usgs.gov/of/2006/1250/pdf/OF06-1250_508.pdf; current access via PURL.
Note
Title from PDF title screen (viewed on Nov. 14, 2006).