ECO chess codes D5 (idea)

D50 - Queen's Gambit Declined/Orthodox Defence
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5

D51
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Nbd7

D52
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Nbd7    
5. e3 c6   
6. Nf3

D53
1. d4 d5   
2. c4 e6  
3. Nc3 Nf6   
4. Bg5 Be7

D54
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7   
5. e3 O-O   
6. Rc1

D55
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7   
5. e3 O-O   
6. Nf3

D56
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7  
5. e3 O-O   
6. Nf3 h6
7. Bh4

D57 - Queen's Gambit Declined, Orthodox Defence, Lasker System
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7   
5. e3 O-O   
6. Nf3 h6
7. Bh4 Ne4   
8. Be7 Qe7   
9. cd5 Nc3   
10. bc3

D58 - Queen's Gambit Declined/Orthodox Defence/Tartakower Variation
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7   
5. e3 O-O   
6. Nf3 h6
7. Bh4 b6

D59
1. d4 d5   
2. c4 e6   
3. Nc3 Nf6   
4. Bg5 Be7   
5. e3 O-O   
6. Nf3 h6
7. Bh4 b6   
8. cd5 Nd5