This is the Winawer Counter-Gambit (ECO--D10, I think).  If unprepared, White can run into a lot of trouble.  That said, White has been scoring rather well of late.  The critical line appears to be: 1 d4 d5 2 c4 c6 3 Nc3 e5 4 dxe5 {This is the main test; White appears to be okay after 4 cxd5 in most lines} d4 5 Ne4 Qa5+ 6 Bd2 Qxe5 7 Ng3 Nf6 {7 ... c5 8 Nf3 Qe7 might be worth a look given what follows} 8 Nf3 Qd6 9 Qc2 Be7 10 0-0-0 0-0 11 Bc3 {11 e3 is the main alternative, played by Kasparov} dxc3 {?!--Burgess.  Maybe 11 ... c5 is better} 12 Rxd6 cxb2+ 13 Qxb2 Bxd6 14 e4 Bf4+ 15 Kb1, and Graham Burgess says this is good for White. 

Another way to play similar variations more safely for Black is to play 1 d4 d5 2 c4 c6 3 Nc3 dxc4 4 e4 e5, though I'm not at all familiar with this line.

I'm sure you'll find decent material on the Winawer Counter-Gambit in most books that deal with the Slav.  I can strongly recommend Graham Burgess's recent book.