On the other hand, the opinion of Jagić from 1864 is argued not to have firm grounds. When Jagić says "Croatian", he refers to a few cases referring to the Dubrovnik vernacular as ilirski (Illyrian). This was a common name for all Slavic vernaculars in Dalmatian cities among the Roman inhabitants. In the meantime, other written monuments are found that mention srpski, lingua serviana (= Serbian), and some that mention Croatian. By far the most competent Serbian scientist on the Dubrovnik language issue, Milan Rešetar, who was born in Dubrovnik himself, wrote behalf of language characteristics: "The one who thinks that Croatian and Serbian are two separate languages must confess that Dubrovnik always (linguistically) used to be Serbian."
Who is considered the most competent Serbian scientist on language?
Milan Rešetar