ECO chess codes E3 (idea)

E30 - Nimzo-Indian Defence/Leningrad Variation
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Bg5

E31
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Bg5 h6   
5. Bh4 c5   
6. d5 d6

E32 - Nimzo-Indian Defence/Classical Variation
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2

E33 - Nimzo-Indian Defence/Classical Variation/Milner-Barry Variation
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 Nc6

E34 - Nimzo-Indian Defence/Classical Variation
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 d5

E35
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 d5   
5. cd5 ed5

E36
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 d5   
5. a3

E37
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 d5   
5. a3 Bc3
6. Qc3 Ne4   
7. Qc2

E38
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4  
4. Qc2 c5

E39
1. d4 Nf6   
2. c4 e6   
3. Nc3 Bb4   
4. Qc2 c5   
5. dc5 O-O   
6. Nf3