If you plan on visiting Montenegro and attend the conference onsite, you must check to see if you need a visa to enter the country. If you are a citizen from one of the countries specified on the following webpage, you do not need a visa to visit Montenegro for 90 days within 180 days: https://visaguide.world/europe/montenegro-visa/. If you are exempt from the visa requirement, you can enter Montenegro with only your passport or ID card depending of the country of your origin. On the other hand, conference delegates from other countries who are requiring a visa to enter Montenegro will be issued an invitation letter by the conference office upon request. The invitation letter will be issued from the host country of the conference. Please note, an invitation letter will only be issued to those participants who have paid the registration fee in full.