Hattin, Donald E., and David A. Darko. “Technique for Determining Coccolith Abundance in Shaly Chalk of Greenhorn Limestone (Upper Cretaceous) of Kansas”. Bulletin (Kansas Geological Survey), no. 202 (January 1, 1971): 1–11. Accessed January 3, 2026. https://journals.ku.edu/kgsbulletin/article/view/22247.