W. Christopher Wozencraft, "Family Ursidae," Mammal Species of the World, (3rd ed.), Don E. Wilson & DeeAnn M. Reeder (ed.), Johns Hopkins University Press, 2005, p. 586-590.
Flynn, J. J.; Finarelli, J. A.; Zehr, S.; Hsu, J.; Nedbal, M. A. (2005). “Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships”. Systematic Biology54 (2): 317–37. doi:10.1080/10635150590923326. PMID16012099.
Flynn, J. J.; Finarelli, J. A.; Zehr, S.; Hsu, J.; Nedbal, M. A. (2005). “Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships”. Systematic Biology54 (2): 317–37. doi:10.1080/10635150590923326. PMID16012099.