Laurin, M & RR Reisz (1996), The osteology and relationships of Tetraceratops insignis, the oldest known therapsid. J. Vert. Paleontol. 16: 95-102. Conrad, J & C Sidor (2001), Re-evaluation of Tetraceratops insignis (Synapsida: Sphenacodontia). J. Vert. Paleontol. 21: 42A (abstract).
Laurin, M & RR Reisz (1996), The osteology and relationships of Tetraceratops insignis, the oldest known therapsid. J. Vert. Paleontol. 16: 95-102. Conrad, J & C Sidor (2001), Re-evaluation of Tetraceratops insignis (Synapsida: Sphenacodontia). J. Vert. Paleontol. 21: 42A (abstract).