
 18: Category theory, homological algebra 
  Category theory, a comparatively new field of mathematics, provides a universal framework for discussing fields of algebra and geometry. 
  While the general theory and certain types of categories have attracted considerable interest, the area of homological algebra has proved most fruitful in areas of ring theory, group theory, and algebraic topology. 
  A full, wideranging text on category theory is by Borceux, Francis: "Handbook of categorical algebra", 3 vol (1: Basic category theory; 2: Categories and structures; 3: Categories of sheaves) (Encyclopedia of Mathematics and its Applications, 502.) Cambridge University Press, Cambridge, 1994. 
 www.math.niu.edu /~rusin/knownmath/index/18XX.html (286 words) 
