Hieronymus, Tobin L.; Witmer, Lawrence M.; Tanke, Darren H.; Currie, Philip J. (September 2009). “The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures”. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology292 (9): 1370–1396. doi:10.1002/ar.20985.