QGA--What do you do if Black tries to keep pawn?

I know its wrong for Black to hold onto the gambit pawn in the Queen's Gambit Accepted but what is the best way for White to proceed? 

For Example:

White to move.

I've played a rapid game 3 days ago where Black tried to hold onto the Pawn with ...c6 and ...b5 and he lost very quickly: http://www.chess.com/livechess/game?id=1231220228

3.Nc3 gives Black chances to keep the pawn (certainly not with 3...b5? though), but 3.Nf3, 3.e4, 3.e3 are all better moves.

Thanx all 4 the help! Checked out Skynet's game, very interesting. Anyone else have games along those lines?

How does black keep the pawn in the 3.Nc3 lines I'm curious.

1.d4 d5 2.c4 dxc4 3.e3 b5 4.a4 and there is no holding on to the pawn for black as far as I know without losing material.

A comical line that many lower rated opponets will fall for.

Doesn't 3.Nc3 allow 3..Qd6 where that isn't blacks best move probably but it looks like it allows them to keep their pawn.

6.Qf3 Nc6 7.Qxc6+ Bd7 8.Qa6 and white should be winning.

When Black knows the trap the line is pointless. I play this:

It's not a trap though...  It is simply a response to the bad move 3..b5 which shouldn't even be played.

4.a4 is the best move as far as I know. 

4.b3 looks weak in comparison.  

nimzobogo you said in your annotations that 3. e4 can lead to a crazy gambit line... What is that line called? I usually play 3. e4 so I want to know just so I'm not caught off guard

The purpose of 3.e3 is to just take the pawn back, the trap is just icing on the cake. It's the most solid option and teas positional with the 3.Nf3 line.

Transpositional I mean.. 3.e3 is just a perfectly good move and no worse than e4.

Trouble with 3. e3 is you've gotta be prepared to play against 3...e5 and get an IQP (although White often gets one anyway in the QGA, but normally gets a bit more compensation when he does)

Engines have shown that ...Be6, hanging on to the pawn, is very difficult to defeat. But if a human were to try it, they'd probably get crushed. Black's position gets very cramped that way.

After 4.Na3 what's the plan to keep the pawn?

As a result of reading the replies to this topic I won the following game.