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- "hypothetico-deductive method." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 16 Nov. 2012. <http://www.britannica.com/EBchecked/topic/280110/hypothetico-deductive-method>.
- "scientific theory." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 16 Nov. 2012. <http://www.britannica.com/EBchecked/topic/528971/scientific-theory>.
- "scientific hypothesis." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. 16 Nov. 2012. <http://www.britannica.com/EBchecked/topic/1775842/scientific-hypothesis>.