Material in the public domain. No restrictions on use.
Creative Commons License
This work has been identified with a Creative Commons Public Domain Mark 1.0.
Beyer, S. W. and Williams, I. A.
"The Geology of Clays,"
Iowa Geological Survey Annual Report:
Vol. 14: p. 377-554.
Available at: http://ir.uiowa.edu/igsar/vol14/iss1/7