↑M. Laurin et R. R. Reisz (1996), "The osteology and relationships of Tetraceratops insignis, the oldest known therapsid," Journal of Vertebrate Paleontology 16(1): 95–102.
↑J. Liu, B. Rubidge, et J. Li (2009), "New basal synapsid supports Laurasian origin for therapsids," Acta Palaeontologica Polonica, 54(3): 393–400.