The ancient sources for the Third Sacred War are scant, and generally lacking in firm chronological information. The main source for the period is Diodorus Siculus's Bibliotheca historica, written in the 1st century BC, which is therefore very much a secondary source. Diodorus is often derided by modern historians for his style and inaccuracies, but he preserves many details of the ancient period found nowhere else. Diodorus worked primarily by epitomizing the works of other historians, omitting many details where they did not suit his purpose, which was to illustrate moral lessons from history; his account of the Third Sacred War therefore contains many gaps.