H4 documents and requirement

[KAMAL299]

Hi,

I am planning to take H4 for my wife, i came to US on may 2011 and now i am working with a client under my employer with a mid employer also involved.

Can you please let me know what are all the documents needed.

and also please clarify

if only the letter from my employer is enough?

or

I have to get letter from My employer , Mid Employer and Client ?

Please clarify....