http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Mineralogy and stratigraphy of the lower part of the Pierre Shale, South Dakota and Nebraska
"Mineralogical data that clarify stratigraphic relations of the Gregory and Crow Creek Members."
Professional paper (Geological Survey (U.S.)) ; 392-B
Studies of the Pierre Shale in the northern Great Plains