Minkowskian geometry and quaternion algebras An exploration of the geometry of quaternion algebra, including a commutative variant which exhibits the properties of Minkowskian geometry.
Non-Euclidean Geometry A historical account with links to biographies of some of the people involved.
References for Non-Euclidean Geometry A bibliographic reference list of books and articles on non-Euclidean geometries, part of the MacTutor History of Mathematics archive.
Smarandache Geometries Having at least one smarandachely denied axiom: validated and invalidated; or invalidated in at least two distinct ways. Discussion groups and meetings.
Spherical Trigonometry, Arc Distance Formula Finding the shortest distance between two points on the earth given latitude and longitude. Download ARC_CALC_3, Microsoft Excel version, A Spherical Triangle Calculator by James Q. Jacobs.
