A very bare-bones piece. The author's sources:

The SITE Institute: Some searching is required. The info on Iraq insurgents isn't gathered into one comprehensive document or even specific section of the website.

International Crisis Group: The link is to their index of Iraq reports, rather than to their home page. I like ICG, but with the exception of one report, which I posted on SWC when it was published, they tend to focus more on the pure political aspects than on the insurgents per se.

That's why I'm surprised he only goes on to list news reports as his final source, and didn't bother with Cordesman's CSIS - they have published a number of in-depth reports looking at the insurgents. I won't even bring up his failure to mention Jane's...