"Annie Jump Cannon." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. 19 Dec. 2009 <http://www.encyclopedia.com>.
"Annie Jump Cannon." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. (December 19, 2009). http://www.encyclopedia.com/doc/1E1-Cannon-A.html
"Annie Jump Cannon." The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved December 19, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-Cannon-A.html