Requirement for business visa to vist a company in China for SriLankan passport holder

one of our machinery supplier from Italy who supplied the similar machinery to China is inviting to show the performance of the machine in China, what we are planinng to purchase.
we received the invitation from the organization in China to vist their manufacturing facility.
please advice what are the other documents required to supmit along with the application form in SriLanka for srilankan passport holder.

your early reply will be highly appriociated