
 PlanetMath: congruence axioms (Site not responding. Last check: 20071027) 
  Crossreferences: properties, mean, axiom, congruent, sides, obvious, angles, triangles, line segments, boundary, closed half plane, line, intersect, lying on, point, ray, satisfies, endpoints, closed line segments, betweenness, ordered geometry, equivalence relation, transitive, imply, symmetric, Reflexive, relation on, relations 
  This is version 6 of congruence axioms, born on 20051008, modified 20051012. 
  (Geometry :: Metric geometry :: Congruence and orthogonality) 
 planetmath.org /encyclopedia/CongruenceAxioms.html (277 words) 
