Possible Duplicates:
Is it appropriate to use short form of “have” ('ve) when it means possession?
Can you contract the main verb in a sentence?
Is we've equivalent to we have?
In some cases, they do seem to be correct, but sometimes they don't. Consider these 4 sentences.
We've got a problem here.
We have got a problem here.
We've a problem here.
We have a problem here.
Which of these are correct, and which are wrong?