Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern South DakotaDOI: info:10.1130/0-8137-2361-2.145v. 361Geological Society of America145–167
Pearson, Dean A., Schaefer, Terry, Johnson, Kirk R., Nichols, Douglas J., and Hunter, John P. 2002. "Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern South Dakota." In The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An Integrated continental record of the end of the Cretaceous ; Special Paper 361. Hartman, Joseph H., Johnson, Kirk R., and Nichols, Douglas J., editors. 145–167. Geological Society of America. 361 https://doi.org/10.1130/0-8137-2361-2.145.