SCHOEWE, Walter H. Coal Resources of the Permian System in Kansas. Bulletin (Kansas Geological Survey), [S. l.], n. 90, p. 54–70, 1951. DOI: 10.17161/kgsbulletin.no.90.22036. Disponível em: https://journals.ku.edu/kgsbulletin/article/view/22036. Acesso em: 6 apr. 2025.