Basically, I'm looking at Freedman, Sociometry 40 (1), 35-41 and at the
boost graph library page:
http://www.boost.org/libs/graph/doc/betweenness_centrality.html Both the paper and the boost web pages mention a normalization factor of
(n-1)(n-2)/2. However the 1/2 factor seems to be missing from the graph-tool
documentation -is this just a documentation typo?