Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction at the Cretaceous-Tertiary boundaryDOI: info:10.1130/0091-7613(2001)029<0039:PCVRFN>2.0.CO;2v. 29No. 139–42
Pearson, Dean A., Schaefer, Terry, Johnson, Kirk R., and Nichols, Douglas J. 2001. "Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction at the Cretaceous-Tertiary boundary." Geology, 29, (1) 39–42. https://doi.org/10.1130/0091-7613(2001)029<0039:PCVRFN>2.0.CO;2.