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.
Keyes, Charles R. "Aboriginal Use of Mineral Coal and Its Discovery in the West." The Annals of Iowa 10 (1912), 431-434.
Available at: http://ir.uiowa.edu/annals-of-iowa/vol10/iss6/6