The paper is very short. He basically applies principles outlined in the first two papers cited to the market over the last year.

"Some distance properties of latent root and vector methods used in multivariate analysis" http://biomet.oxfordjournals.org/cgi/content/abstract/53/3-4...

"Hierarchical StructureinFinancial Markets" http://arxiv.org/pdf/cond-mat/9802256

The first is behind a journal wall, but if you're at a university you should probably have access. The second is free for everyone! Yay.