"bloodroot." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. 6 Nov. 2009 <http://www.encyclopedia.com>.
"bloodroot." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. (November 6, 2009). http://www.encyclopedia.com/doc/1E1-X-bloodroo.html
"bloodroot." The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved November 06, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-X-bloodroo.html