Thxs for the answers so far and the useful hints!

I analysed the 5. ...Na6 a little bit, quite difficult for black, but maybe there is some help in the odd line 9. ... Nd6!?

1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 c5 5. dxc5 Na6 6. a3 Bxc3+ 7. Qxc3 Nxc5 8. b4 Nce4 9. Qb2 $1 (9. Qd4 d5 10. c5 b6 11. f3
bxc5 12. bxc5 Qa5+ 13. Qb4 Qc7 $44) 9... d5 (9... Nd6 $5 10. c5 Nc4 11. Qd4 d5 $13) 10. c5 d4 (10... Nh5 11. g3 f5 12. Nf3 O-O 13. Bg2 Bd7 (13... b6 14. c6 Qd6 15. Ne5 Ba6 16. a4) 14. Ne5 a5 15. O-O axb4 16. axb4 Rxa1 17. Qxa1 $16) 11.e3 Ng4 (11... e5 12. exd4 exd4 13. Bd3 O-O 14. Ne2 Nc3 15. O-O $1 Nxe2+ 16.Qxe2 Re8 17. Qc2 $16) 12. Nh3 dxe3 13. Qxg7 Ke7 14. Ng5 exf2+ 15. Ke2 Qd5 16.
Qxf7+ Kd8 17. Qf3 $1 $16 (17. Qg7 Bd7 $44)

#4 is absolutely mainstream, so no doubts about that one. Learn about it in Dearing's book "Play the Nimzo-Indian".

#1 is thought to be dubious, but may be playable. It's treated in Vigorito's "Challenging the Nimzo-Indian".

I don't know the status of #2, but I would be surprised if it has been refuted. It's just that the plan Bxc3, d6 and e5 is much more popular at high levels and therefore steals the limelight.

#3 is worth investigation, as many other sidelines in the 5. g3 Nimzo.
Wards book "Nimzo-Indian Kasparov System" is the right book for learning these 4. Nf3 lines.

I'm playing The Nimzo- and Queen's Indians _and_ the Slav! No reason to abandon the Slav for the Nimzo. Play both! You will be less predictable and more annoying!

 
Hi all,

I´m a little bit bored with the slav, so I wanna switch to Nimzo. My theory knowledge is clearly outdated, so I ask the forum, if the following lines are still playable for black:

#1
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 c5 5. dxc5 Na6
6. a3 Bxc3+ 7. Qxc3 Nxc5 8. b4 Nce4 9. Qd4 (9. Qb2 d5) 
9... d5 10. c5 (10. cxd5) 

#2
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Bg5 c5 5. d5 b5

#3
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 c5 5. g3 Ne4 6.Qd3 Qa5 7. Qxe4 Bxc3+ 

#4
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 b6 

Which books/DVD do you recommend to study?