Sawin, Robert S., Ronald R. West, Evan K. Franseen, W. Lynn Watney, and James R. McCauley. “Carboniferous-Permian Boundary in Kansas, Midcontinent, U.S.A”. Bulletin (Kansas Geological Survey), no. 252 (January 1, 2002): 1–13. Accessed January 6, 2026. https://journals.ku.edu/kgsbulletin/article/view/20384.