Krause, J., Unger, T., Nocon, A., Malaspinas, A.-S., Kolokotronis, S.-O., Stiller, M., et al. (2008). Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene-Pliocene boundary. BMC Evolutionary Biology, 8: 220. doi:10.1186/1471-2148-8-220.