user2042: I wish to play a specific move order of the QGD as Black, but the problem is that White can throw Marshall gambit at me. 
I do not want to play the sharp lines, I need a solid and fully equal position.
I have tried to introduce novelties two times ( I even asked for help here both times ), but both of them failed since I was able to refute them in my home analysis after careful work ( that is why I have deleted the mentioned questions ). Therefore I have given up on trying to improve the opening and am asking for help.
This is the move order I have in mind:
[fen ""]

1.d4 d5 2.c4 e6 3.Nc3 c6 4.e4!?

This is known as Marshall gambit. As I have said earlier, I do not wish to accept it, I need solid quiet positional lines. Something like 4...dxe4 5.Nxe4 Nd7 could work for me, as it is similar to Caro-Kann. The way things stand now, this line is good for White and both of my attempts to improve it have failed, as stated above.
To summarize my questions:

Is there a way for Black to decline the gambit and reach full equality ?
If there is a positive answer to the first question, can you recommend some high quality resources for studying such lines ( books/online resources etc ) ?

NOTE:
I would not mind if in the above mentioned position Black can transpose into another opening, as long as it is solid one.
Thank you for your help. 
Best regards.

user2429: 
Is there a way for Black to decline the gambit and reach full equality
  ?

Normally, it's hard to prove a negative, but after analyzing Black's options (and having some fun analyzing the lines with 4...Nf6), I have to say that there is no solid way to achieve equality for Black by declining the gambit. 
Black's only chance at achieving equality is with 4...Bb4!? , but the kind of open positions that result from 4...Bb4 are not the ones you would describe as "solid" for Black". 
So my answer is no, Black cannot achieve equality by declining the gambit, unless Black's attempts at dynamic equality with 4...Bb4. 
    [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

    1. d4 d5 2. c4 c6 3. Nc3 e6 4. e4 Nf6 (4... a6 5. Nf3 b5 6. exd5 exd5 7. cxd5
    cxd5 8. Bd3 Be7 9. O-O Nf6 10. Bf4 Nc6 11. Rc1 Bb7 12. Nxb5 axb5 13. Bxb5 Rc8
    14. Ne5 Qb6 15. Qb3 O-O 16. Bxc6 Qxb3 17. axb3) (4... Bb4 5. cxd5 cxd5 6. exd5
    exd5 7. Nf3 Nf6 8. Bd3 O-O 9. O-O) (4... Nd7 5. cxd5 cxd5 6. exd5 exd5 7. Nxd5)
   (4... f5 5. exd5 exd5 6. cxd5 cxd5 7. Bb5+ Nc6 8. Qh5+ g6 9. Qe2+ Be7 10. Nf3
    Nf6 11. Bh6 Ne4 12. O-O Be6 13. Ne5 Qb6 14. Rac1 Rc8 15. Rfd1 a6 16. Bxc6+ bxc6
    17. f3 Nxc3 18. Rxc3 c5 19. Rb3 Qd6 20. Bf4 cxd4 21. Nxg6 d3 22. Rbxd3 Qc5+ 23.
    Be3 Qb5 24. Nxh8) (4... g6 5. Nf3 Bg7 6. Bf4 Ne7 7. h4 Nd7 8. h5) 5. e5 Ne4 6.
    Bd3 (6. Nxe4 dxe4 7. Ne2 c5 8. d5 Nd7 9. dxe6 Nxe5 10. exf7+ Nxf7 11. Be3) 6...
    Nxc3 7. bxc3 dxc4 8. Bxc4 c5 9. Nf3 cxd4 10. cxd4 Nc6 11. O-O Be7 12. Qd3 O-O
    13. Qe4 Nb4 14. Rb1 Bd7 (14... a5 15. Qg4 Kh8 16. a3 Qc7 17. Bb5 Nd5 18. Bd3
    Qc3 19. Rd1 g6 20. Bh6 Rd8 21. Bg5 Qxa3 22. Ra1 Qb4 23. Rdb1 Qc3 24. Bxe7 Nxe7
    25. Qh4 Rd7 26. Ng5 h5 27. Nxf7+ Kg8 28. Rd1 Kxf7 29. Rac1 Qb4 30. Qf6+ Kg8 31.
    Qxe6+ Kg7 32. Qf6+ Kh7 33. e6 Rd5 34. Qf7+ Kh8 35. Rc7 Bxe6 36. Qf6+ Kg8 37.
    Qxe6+ Kf8 38. Bxg6 Rf5 39. Bxf5) 15. Rxb4 $5 Bxb4 16. Ng5 g6 17. Qh4 (17. d5 $5
    ) 17... h5 18. g4 Qe7 19. Be3 Rac8 20. Bb3 a5 21. gxh5 a4 22. Bd1 Kg7 23. hxg6
    Rh8 24. Qe4 fxg6 25. Qxb7 Rb8 26. Qe4 Ba3 27. Bc2 Qe8 28. Qg4 Rb2 29. Bd3 Rxa2
    30. Bc4 Rb2 31. Bxe6 Bxe6 32. Nxe6+ Kg8 33. Nf4 Rb7 34. Ra1 Bf8 35. Nd5 Kf7 36.
    Qe4 Qe6 37. Nf4 Qg4+ 38. Kf1 Rb6 39. h3 Qf5 40. Qxf5+ gxf5 41. Rxa4


user924: I don't know really know the theory here, but I can give some pointers. Maybe they are of some use for you or other readers.
The setup with c6/d5/e6 in the first three moves against white's d4 and c4 is called the Triangle; usually black wants to aim for the Noteboom variation (1.d4 d5 2.c4 c6 3.Nc3 e6 4.Nf3 dxc4 and roll with the queenside pawns).  4.e4 is white's most ambitious and sharp way to attack the Triangle. After 4.e4, you won't see any transpositions to other well-known openings.
If you're not looking for sharp lines, this is a bit of an odd move order to play, because besides the sharp Noteboom there's also this sharp Marshall Gambit to deal with. The Slav and QGD both offer better chances of a solid positional game than the Triangle, I think.
Scherbakov's book The Triangle System won awards and got great reviews; if you're going to play this seriously, that book should be your #1 source.
Black's main option besides accepting the gambit is 4...Bb4; the position looks a bit like a French Winawer (1.e4 e6 2.d4 d5 3.Nc3 Bb4) with the c-pawns on different squares. According to Scherbakov, "White does have a few ways to obtain a small edge, but Black's position remains playable." He also explains that play is rather different from normal Slav positions, and then spends 8 pages discussing it.
I general I suspect that as black, guaranteed quiet play and complete equality is a bit too much to expect in any opening. If you want to dodge white's sharpest options, you're going to have to make some concessions.

2042: <p>I wish to play a specific move order of the QGD as Black, but the problem is that White can throw Marshall gambit at me. </p>

<p>I do not want to play the sharp lines, I need a solid and <strong>fully equal</strong> position.</p>

<p>I have tried to introduce novelties two times ( I even asked for help here both times ), but both of them failed since I was able to refute them in my home analysis after careful work ( that is why I have deleted the mentioned questions ). Therefore I have given up on trying to improve the opening and am asking for help.</p>

<p>This is the move order I have in mind:</p>

<pre><code>[fen ""]

1.d4 d5 2.c4 e6 3.Nc3 c6 4.e4!?
</code></pre>

<p>This is known as Marshall gambit. As I have said earlier, I do not wish to accept it, I need solid quiet positional lines. Something like <code>4...dxe4 5.Nxe4 Nd7</code> could work for me, as it is similar to Caro-Kann. The way things stand now, this line is good for White and both of my attempts to improve it have failed, as stated above.</p>

<p>To summarize my questions:</p>

<ol>
<li>Is there a way for Black to decline the gambit and reach <strong>full equality ?</strong></li>
<li>If there is a positive answer to the first question, can you recommend some high quality resources for studying such lines ( books/online resources etc ) ?</li>
</ol>

<p><em>NOTE:</em></p>

<p>I would not mind if in the above mentioned position Black can transpose into another opening, <strong>as long as it is solid one.</strong></p>

<p>Thank you for your help. </p>

<p>Best regards.</p>
 2429: <blockquote>
  <p>Is there a way for Black to decline the gambit and reach full equality
  ?</p>
</blockquote>

<p>Normally, it's hard to prove a negative, but after analyzing Black's options (and having some fun analyzing the lines with <strong>4...Nf6</strong>), I have to say that there is no <strong><em>solid</em></strong> way to achieve equality for Black by declining the gambit. </p>

<p>Black's only chance at achieving equality is with <strong>4...Bb4!?</strong> , but the kind of open positions that result from <strong>4...Bb4</strong> are not the ones you would describe as "<strong>solid</strong>" for Black". </p>

<p>So my answer is no, Black cannot achieve equality by declining the gambit, unless Black's attempts at dynamic equality with <strong>4...Bb4</strong>. </p>

<pre><code>    [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

    1. d4 d5 2. c4 c6 3. Nc3 e6 4. e4 Nf6 (4... a6 5. Nf3 b5 6. exd5 exd5 7. cxd5
    cxd5 8. Bd3 Be7 9. O-O Nf6 10. Bf4 Nc6 11. Rc1 Bb7 12. Nxb5 axb5 13. Bxb5 Rc8
    14. Ne5 Qb6 15. Qb3 O-O 16. Bxc6 Qxb3 17. axb3) (4... Bb4 5. cxd5 cxd5 6. exd5
    exd5 7. Nf3 Nf6 8. Bd3 O-O 9. O-O) (4... Nd7 5. cxd5 cxd5 6. exd5 exd5 7. Nxd5)
   (4... f5 5. exd5 exd5 6. cxd5 cxd5 7. Bb5+ Nc6 8. Qh5+ g6 9. Qe2+ Be7 10. Nf3
    Nf6 11. Bh6 Ne4 12. O-O Be6 13. Ne5 Qb6 14. Rac1 Rc8 15. Rfd1 a6 16. Bxc6+ bxc6
    17. f3 Nxc3 18. Rxc3 c5 19. Rb3 Qd6 20. Bf4 cxd4 21. Nxg6 d3 22. Rbxd3 Qc5+ 23.
    Be3 Qb5 24. Nxh8) (4... g6 5. Nf3 Bg7 6. Bf4 Ne7 7. h4 Nd7 8. h5) 5. e5 Ne4 6.
    Bd3 (6. Nxe4 dxe4 7. Ne2 c5 8. d5 Nd7 9. dxe6 Nxe5 10. exf7+ Nxf7 11. Be3) 6...
    Nxc3 7. bxc3 dxc4 8. Bxc4 c5 9. Nf3 cxd4 10. cxd4 Nc6 11. O-O Be7 12. Qd3 O-O
    13. Qe4 Nb4 14. Rb1 Bd7 (14... a5 15. Qg4 Kh8 16. a3 Qc7 17. Bb5 Nd5 18. Bd3
    Qc3 19. Rd1 g6 20. Bh6 Rd8 21. Bg5 Qxa3 22. Ra1 Qb4 23. Rdb1 Qc3 24. Bxe7 Nxe7
    25. Qh4 Rd7 26. Ng5 h5 27. Nxf7+ Kg8 28. Rd1 Kxf7 29. Rac1 Qb4 30. Qf6+ Kg8 31.
    Qxe6+ Kg7 32. Qf6+ Kh7 33. e6 Rd5 34. Qf7+ Kh8 35. Rc7 Bxe6 36. Qf6+ Kg8 37.
    Qxe6+ Kf8 38. Bxg6 Rf5 39. Bxf5) 15. Rxb4 $5 Bxb4 16. Ng5 g6 17. Qh4 (17. d5 $5
    ) 17... h5 18. g4 Qe7 19. Be3 Rac8 20. Bb3 a5 21. gxh5 a4 22. Bd1 Kg7 23. hxg6
    Rh8 24. Qe4 fxg6 25. Qxb7 Rb8 26. Qe4 Ba3 27. Bc2 Qe8 28. Qg4 Rb2 29. Bd3 Rxa2
    30. Bc4 Rb2 31. Bxe6 Bxe6 32. Nxe6+ Kg8 33. Nf4 Rb7 34. Ra1 Bf8 35. Nd5 Kf7 36.
    Qe4 Qe6 37. Nf4 Qg4+ 38. Kf1 Rb6 39. h3 Qf5 40. Qxf5+ gxf5 41. Rxa4
</code></pre>
 924: <p>I don't know really know the theory here, but I can give some pointers. Maybe they are of some use for you or other readers.</p>

<p>The setup with c6/d5/e6 in the first three moves against white's d4 and c4 is called the <em>Triangle</em>; usually black wants to aim for the <em>Noteboom</em> variation (1.d4 d5 2.c4 c6 3.Nc3 e6 4.Nf3 dxc4 and roll with the queenside pawns).  4.e4 is white's most ambitious and sharp way to attack the Triangle. After 4.e4, you won't see any transpositions to other well-known openings.</p>

<p>If you're not looking for sharp lines, this is a bit of an odd move order to play, because besides the sharp Noteboom there's also this sharp Marshall Gambit to deal with. The Slav and QGD both offer better chances of a solid positional game than the Triangle, I think.</p>

<p>Scherbakov's book <em>The Triangle System</em> won awards and got great reviews; if you're going to play this seriously, that book should be your #1 source.</p>

<p>Black's main option besides accepting the gambit is <em>4...Bb4</em>; the position looks a bit like a French Winawer (1.e4 e6 2.d4 d5 3.Nc3 Bb4) with the c-pawns on different squares. According to Scherbakov, "White does have a few ways to obtain a small edge, but Black's position remains playable." He also explains that play is rather different from normal Slav positions, and then spends 8 pages discussing it.</p>

<p>I general I suspect that as black, guaranteed quiet play <em>and</em> complete equality is a bit too much to expect in any opening. If you want to dodge white's sharpest options, you're going to have to make some concessions.</p>
