University of St. Andrews (UK)
University of St. Andrews: Luther Pfahler Eisenhart
The School of Mathematics and Statics at the University of St. Andrews, Scotland, presents this article on the life and work of Luther Eisenhart (1876-1965 CE). Eisenhart, an American mathematician who lived well into the 20th century,...
Wolfram Research
Wolfram Mathworld: Elliptic Geometry
MathWorld offers a brief definition of elliptic geometry and including a brief discussion of its relationship to Euclidean geometry, with links to other related definitions.
Math Words
Math words.com: Elliptic Geometry
The basic definition for what elliptic geometry is is found here.