Unrelated:

Every chapter of Romans has at least three Old Testament references.  It would be so interesting to see this kind of graph applied to Romans & the OT.

It would be even more interesting to see an Old Testament, New Testament graph like this.

Because, really, if you want to know the New Testament, you’ve got to know the Old Testament, and such a presentation of the data would show that so clearly.  (Probably someone has already done this, I just can’t get the search terms right it on google or flickr.)