Jefferson, T. A.; Leatherwood, S.; Webber, M. A. (1994). Marine Mammals of the World. Food and Agriculture Department of the United Nations. pp. 1–2. ISBN 978-92-5-103292-3. OCLC 30643250.
Jefferson, T. A.; Webber, M. A.; Pitman, R. L. (2009). Marine Mammals of the World A Comprehensive Guide to their Identification (1st ed.). London: Academic Press. pp. 7–16. ISBN 978-0-12-383853-7. OCLC 326418543.
