I thought that Gallagher did a decent job covering this line (from the Black side) in one of his books, but I'm not sure which one it was.  It may have been Play the King's Indian or Beating the Anti-King's Indians.  Not much help for the White side, I'm afraid. 

I always feel that this type of system can score very well in practice.  Essentially White is being as annoying as possible: in the King's Indian, White most often plays the moves d2-d4, c2-c4, and e2-e4, which leave the d4-square very weak.  Most of Black's counterplay (at least early on) comes by playing against this square, i.e. ...Bg7, ...e7-e5, and ...Nc6, for instance.  When White plays 6.e3, he takes away Black's standard source of counterplay.  Black now has to come up with something different than normal, and in a practical game without preparation he may not be up to the task.  I think that this is what accounts for White's good score in this line more than anything else.

On the other hand, it's good chess, if a bit simple.  Petrosian played some great games in this line as well as Smyslov.  If you're looking to do some work on your own, I'd suggest playing through and studying Akobian's games in a database; it helps to find a "weaker" grandmaster's games for study and ideas to adopt, as they aren't nearly as widely known.  And yes, my tongue was very much in my cheek; "weaker" GMs are still very strong and a lot can be gained from studying their games.  

Incidentally, I'd start with these two videos to see if this system interests you; even if it doesn't they're excellent lessons in middlegame play:

http://www.youtube.com/watch?v=h80Mu4N6oYI
http://www.youtube.com/watch?v=X7RP0-lre_c

I see that White's statistics do look quite good in the online NIC database (in the position after 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. Nf3 0-0 5. Bg5 d6 6. e3, it appears that he scores from about 58% to 70% depending on Black's choice of subvariation).  But what about the performance ratings, i.e. could this result from the Smyslov being played disproportionately by higher-rated players as White against lower-rated players? 

I can't recall any material of the type you're after, which seems rather curious.  The main thing I think of is John Watson's "Unconventional King's Indian" (which has about 11 pages on it, but thinks Black has various ways to equalize).  Oh, there was a book (from maybe 15-20 years ago, i.e. somewhat older than Watson's) by a Hungarian FM (Egon Varnusz; he wrote a book on Portisch's games some time ago) I believe called "Anti-Indian Systems" which might be a possibility.