E-mail:

Further to the F visa, looks like Bill has to apply the Invitation Letter for the 4 students - China is not lifting the restrictive F visa as yet.

Below is an email where you can apply for the Invitation Letter - apparently, the company has to apply from where the company registered its business name.

Invitation letter is equal a need to wait thing againnn! Urrrrghhh! =(
Patience.
If the offer letter was gotten earlier, this thing really could be an avoidable thing, seriously.