I get "Access forbidden" at the link in #1 (sci.utah.edu/~weiliu/research/clustering_fmri/…)

I still don't follow. Do we consider the indeterminate case to mean "not correlated"? Let's take 3 vectors: a = [1 9 1 9 1], b = [9 1 9 1 9], c = [5 5 5 5 5]. a and b should have some negative correlation. I would have said that (a and c) and also (a and b) had zero correlation, but I guess we have seen that they actually have "indeterminate" correlation. How would you check for this in software? Just set the correlation to zero if either the numerator or denominator are < epsilon (say 1e-5 or something)? Isn't there some quantity that would behave more like I am expecting?