Complex sentence: The Baška tablet is the first complete document we have on the language of the people with elements of literal Church Slavonic, and is often regarded as the "birth certificate" of the Croatian language, with the first mention of the "Croats".
Split into simpler sentences: The Baška tablet is the first complete document we have on the language of the people with elements of literal Church Slavonic. It is often regarded as the "birth certificate" of the Croatian language, and carries the first mention of the "Croats".