obtain a business visa to China from Sri Lanka

Dear, I am a Snr Manager attached to a multinational company, Sri Lanka. I have traveled to Chine twice obtaining business M type. i am planning to visit the exhibition of CPhl, ICSE, P-MEC & LAB World cHINA 2016 exhibition and i have received an invitation letter from the organiser, China Chamber of Commerce for Import and Export of Medicines & Health Products for me to visit the exhibition. The invitation letter mentioned all the required information under a company letterhead. pl let me know whether the said invitation letter with the other required documents are ok for me to obtain business M type? Do i still have to submit an original letter of duly authorized notice (red notice) together with other required docs to obtain a business M type from Sri Lanka?