Campbell, Neil A.; Brad Williamson; Robin J. Heyden. Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. 2006 [2015-01-11]. ISBN 0-13-250882-6. (原始内容存档于2014-11-02).
存档副本. The Columbia Encyclopedia, Sixth Edition. Columbia University Press. 2004 [2011-05-16]. (原始内容存档于2011-10-27).
Campbell, Neil A.; Brad Williamson; Robin J. Heyden. Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. 2006 [2015-01-11]. ISBN 0-13-250882-6. (原始内容存档于2014-11-02).