Hill, Jr., Walter E., William B. Hladik, and Wanda N. Waugh. “Preliminary Report on the Beneficiation of Some Kansas Clays and Shales”. Bulletin (Kansas Geological Survey), no. 165 (December 31, 1963). Accessed December 30, 2025. https://journals.ku.edu/kgsbulletin/article/view/21145.