 Crucially though, the "lingua franca" at the time among Slavic elites in the Ottoman Empire was still Old Church Slavonic.For Italians traveling through to Istanbul, the language of the Slavic Croats was often the only exposure they had to any of the Slavic languages; indeed, Bulgarian and Macedonian dialects were far more common in Istanbul than Croatian.Within the territory of the present Republic of Croatia, Muslim believers were registered for the first time during the 1931 census