Nimzo-Indian Defense: Classical, Noa Variation

1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Qc2 d5 5.a3 Bxc3+ 6.Qxc3 O-O 7.Bg5 dxc4 8.Qxc4 b6 9.Rd1