Williamson, T.E. & Kirkland, J.I. & Lucas, S.G. (1993)
Selachians from the Greenhorn cyclothem («Middle» Cretaceous: Cenomanian-Turonian), Black Mesa, Arizona, and the paleogeographic distribution of late Cretaceous selachians. Journal of Paleontology, 67(3), 447–474

Williamson, T.E. & Lucas, S.G. (1993)
Freshwater selachians from the early Palaeocene of the San Juan Basin, north-western Mexico, USA. Tertiary Research, 14(3), 97–105

Williamson, T.E. & Lucas, S.G. & Kirkland, J.I. (1991)
The Cretaceous Elasmobranch Ptychodus decurrens from North America. Geobios, 24(5), 595–599
DOI: 10.1016/0016-6995(91)80023-S

Williamson, T.E. & Lucas, S.G. (1990)
New Cretaceous vertebrates from the Mulatto Tongue of the Mancos Shale, central New Mexico. New Mexico Journal of Science, 30, 27–34

Williamson, T.E. & Lucas, S.G. & Pence, R. (1989)
Selachians from the Hosta Tongue of the Point Lookout Sandstone (Upper Cretaceous, Santonian), central New Mexico. New Mexico Geological Society Guidebook, 40, 239–245