In this exposition we give a simple and complete treatment of A. Knutson and
T. Tao's recent proof (http://front.math.ucdavis.edu/math.RT/9807160) of the
saturation conjecture, which asserts that the Littlewood-Richardson semigroup
is saturated. The main tool is Knutson and Tao's hive model for
Berenstein-Zelevinsky polytopes. In an appendix of W. Fulton it is shown that
the hive model is equivalent to the original Littlewood-Richardson rule.Comment: Latex document, 12 pages, 24 figure
