
 Preface to SemiRiemannian Geometry (Site not responding. Last check: 20071020) 
  The principal special cases are Riemannian geometry, where the metric is positive definite, and Lorentz geometry. 
  After establishing the requisite language of manifolds and tensors (Chs.1 and 2), the plan of the book is to develop the foundations of semiRiemannian geometry in the simplest way and without regard to signature, allowing the Riemannina and Lorentz cases to appear as needed (Chs.35 and 7). 
  The fact that relativity theory is expressed in terms of Lorentz geometry is lucky for geometers, who can thus penetrate surprisingly quickly into cosmology (redshift, expanding universe, and big bang) and, a topic no less interesting geometrically, the gravitation of a single star (perihelion advance, bending of light, and fl holes). 
 www.math.ucla.edu /~bon/srgpreface.html (402 words) 
