Boardman , D. R. I., Work, D. M. ., Mapes, R. H. ., & Barrick, J. E. . (1994). Biostratigraphy of Middle and Late Pennsylvanian (Desmoinesian-Virgilian) ammonoids. Bulletin (Kansas Geological Survey), 232, 1-96. https://doi.org/10.17161/kgsbulletin.no.232.20477