On frequent travels, Mihanović visited bookshops, monasteries and convents, researching old documents and manuscripts in South Slavic languages. He saved some of the writings from Greek monasteries because the Greeks used these old papers, which were unimportant to them, to make paper cones or light fires with them. The Glagolitic manuscripts “Codex Zographensis” from the late 10th century and “Mihanović’s paragraf from the Apostles” from the 12th century are among his most important discoveries. Mihanović’s collection of Old Slavic manuscripts is kept today in Croatian Academy of Sciences and Arts.