Smith, D. (1906). Article 7: Substitutions and Groups. History of Modern Mathematics (Lit2Go Edition). Retrieved June 19, 2013, from http://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1732/article-7-substitutions-and-groups/
Smith, David Eugene. "Article 7: Substitutions and Groups." History of Modern Mathematics. Lit2Go Edition. 1906. Web. <http://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1732/article-7-substitutions-and-groups/>. June 19, 2013.
David Eugene Smith, "Article 7: Substitutions and Groups," History of Modern Mathematics, Lit2Go Edition, (1906), accessed June 19, 2013, http://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1732/article-7-substitutions-and-groups/.