Bleg: Know any good referee studies?

I've been invited to this year's MIT Sloan Sports Analytics Conference, to participate in the "Referee Analytics" panel. I guess if I'm going to be talking about refereeing, I should try to get up to date on some of the research that's been going on.

So, a bleg: could you guys refer me, either in the comments or online, to what you think is important research on refereeing/umpiring in any sport? Much appreciated.

Oh, and speaking of umpiring ... a couple of years back, I had a nine-post analysis of the study about umpires and racial discrimination. Recently, I distilled those posts into an article that ran in the Fall, 2010 issue of SABR's "Baseball Research Journal."

Here's a .PDF of that article. I recommend it over my original posts ... back then, I was trying to figure it out as I was going along. This article is a distillation of the analysis, and what I actually concluded. (If you do want the original posts, they're linked at my website.)

And, by the way, SABR has an archive of past BRJ articles. It's a pretty good resource. There's at least one Bill James piece, for instance.