Documents require for applying Chinese supplier visit.

Hi, I have been selected for supplier VISIT in Chin from my company and would like to know what kind of documents I need for applying VISA other than following documents.

1) VISA application form
2) Releasing letter form my current company for the visit
3) Invitation letter from the supplier with government approved red seal

So can you pls check and advice whether I need to arrange any other letter other than above?