You can only look up names on the national domains, .RS and .СРБ, under the following second-level domains: .RS, .CO.RS, .ORG.RS, .IN.RS, .EDU.RS, .СРБ, .ПР.СРБ, .ОРГ.СРБ, .ОБР.СРБ, .ОД.СРБ
Serbian National Internet Domain Registry
Žorža Klemansoa 18а/I, Belgrade, Serbia