Complex sentence: The letters of Avitus are of considerable importance for the ecclesiastical and political history of the years between 499 and 518, as primary sources of early Merovingian political, ecclesiastical, and social history.
Split into simpler sentences: The letters of Avitus are of considerable importance for the ecclesiastical and political history of the years between 499 and 518. His letters are also among the important primary sources of early Merovingian political, ecclesiastical, and social history.