An FAQ guideline from Ministry of Home Affairs, India regarding issue of VISA is available here.
Some embassy might require the letter from the Indian Government approving the Conference. Please click below links to download approval letters from Ministry of Home Affairs, Ministry of External Affairs and Ministry of Human Resource Development (MHRD):
Security Clearance: to be updated soon
Political Clearance: to be updated soon.
Clearance from MHRD: to be updated soon.