↑ CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN 978-0-8493-4258-5.
↑ Madge, Steve, Waterfowl: An Identification Guide to the Ducks, Geese, and Swans of the World. Houghton Mifflin Harcourt (1992), ISBN 978-0-395-46726-8
↑ Mondadori, Arnoldo, ed. (1988). Great Book of the Animal Kingdom. New York: Arch Cape Press. p. 183.
