Non-Euclidean Geometry

This area covers all kinds of point-line-geometries which do not satisfy Euclid's Axiom of Parallelity. It includes hyperbolic and projective geometry.

References

1. David Hilbert: Grundlagen der Geometrie. Mit Supplementen von Paul Bernays. Herausgegeben und mit Anhaengen versehen von Michael Toepell, 14. Aufl. (German), Teubner-Archiv zur Mathematik. Supplement. 6. Stuttgart: B. G. Teubner (1999).
2. H.S.M. Coxeter: Non-Euclidean geometry, 6th ed., Spectrum Series. Washington, DC: The Mathematical Association of America (1998).