Participants requiring an entry visa to attend the conference are encouraged to apply well in advance (reccommended 2 months in advance). You can check the page here to see if you need a visa:
https://welcometoserbia.gov.rs/discovery-tool
Official invitation letters can be issued to registered participants upon request to support their visa application. Please contact the conference organizers after completing your registration.
For the citizens of most European countries, USA, Canada, Australia, New Zealand and most of South America countries an entry visa is not required. In some cases an invitation letter might be necessary; it can be sent, upon request, by LOC. Citizens of other countries are advised to contact the nearest Serbian consular Office in their countries for information about visa requirements. You can also check Welcome to Serbia portal for visa instructions.