Smith, D. (1906). Article 18: Non-Euclidean Geometry. History of Modern Mathematics (Lit2Go Edition). Retrieved February 13, 2026, from https://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1743/article-18-non-euclidean-geometry/
Smith, David Eugene. "Article 18: Non-Euclidean Geometry." History of Modern Mathematics. Lit2Go Edition. 1906. Web. <https://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1743/article-18-non-euclidean-geometry/>. February 13, 2026.
David Eugene Smith, "Article 18: Non-Euclidean Geometry," History of Modern Mathematics, Lit2Go Edition, (1906), accessed February 13, 2026, https://etc.usf.edu/lit2go/103/history-of-modern-mathematics/1743/article-18-non-euclidean-geometry/.