A common response to Black opening with on the 5-4 point is White to invade at the 3-4 point with (4-5 point 4-3 approach). Black attaches "on the outside" with , White hane's with , Black quietly backs off with , and White connects to the outside with .
Although a is a common next move, see the following diagram for another possibility.
Black can turn at instead of cutting. After Black cuts at and White connects with , is a well-timed jab.
Care to guess what White should do ?
In this case it would be wrong for White to capture a stone by playing at  .
Instead, White should come out with . Black connects out with , White turns with , Black runs twice with and .
However, the interesting reading question comes up here.
It can be verified that if White presses once more with c, Black can kill White in the corner by responding at b .
Hence after Black , White should make life by attaching at a  .
The fact that Black was supposed to play a instead of attacking with implies that is too aggressive.
How should White take advantage now ?
As far as I can tell, the Get Strong at Joseki 2 book does not answer this question, but since the book does say Black should play a instead of , the question begs to be answered.
Please place your answers below.
unkx80: My intuition calls for this. Needs verification.
Eric Osman: Looks like a good start, but can't Black put up a more interesting fight with a instead of ?