Safety Order No. 03/2021 relating to limitations of the use of airspace in wider area of the Belgrade, as from 10th October 2021 till 15thOctober 2021 can be found on this link  Requirements for entry into the Republic of Serbia, including information for passengers arriving from State with special risk from spreading COVID-19 contagious disease,  and travelling abroad can be found on Ministry of Foreign Affairs’ web page Information for passengers regarding conditions for entering Republic of Serbia are available in the form of NOTAM and can be found on Serbia and Montenegro Air Traffic Agency website - link  On March 12, 2020, the Civil Aviation Directorate of the Republic of Serbia issued an Operational Notice regarding the implementation of safety measures requiring public air transport operators to provide sufficient disinfectants to prevent the spreading of COVID-19   
Air Traffic Safty Electronics Personnel - ATSEP
  1. Record of Air Traffic Safety Eletronics Personnel Training Organization