I'm not an expert on this line, but I think the reason for Black playing ...b6 and then ...b5 a couple of moves later is to try and take the sting out of a4. Therefore, it seems more logical to play 12.a4 instead of 12.Qd2 because without a4 it is very difficult to put pressure on Black's position, as the pressure on the e4-pawn is too strong for f4 to be a serious option. 

In my opinion, the position after 12.a4 b4 13.Nd5 Nd5 14.ed5 Nd7 15.c3 bc3 16.bc3 Bg5 17.Bf2 Qc7 18.c4 is slightly better for White, as it is difficult for Black to get his majority going on the kingside with a future ...f5 and ...e4 being well met by Nd4. On the queenside, White should be able to get c5 in eventually, as if Black plays ...Nc5, then taking on c5 will provide White with a protected passed d-pawn.

In comparison, after 12.Qd2, the position after 12...Nbd7 13.Rfd1 Rc8 14.a4 b4 15.Nd5 Nd5 16.ed5, Black can play 16...Nf6 17.Qb4 Nd5 18.Qb7 Ne3 19.Rd2 Nc2 and if anyone is better, it is Black. 13.Rfc1 may be somewhat better but still can't offer more than equality. 

In terms of references, I don't know of any books covering this variation, but ECO, Informant and the Yearbooks are good places to start.