Ancient authors: Ephoros of Kyme (FGrHist / BNJ 70 F119) as cited by Strabo, Geography 9.2.3 (link to Greek text and full English translation).
Comments: Ephoros (or: Ephorus) of Kyme’s works (ca. 340 BCE) survive only in brief citations by others, and in this case Strabo (before 18 CE) cites Ephoros’ views on Phoenician settlers in Boiotia.
Source of the translation: H.L. Jones, Strabo, vol. 4 (LCL; Cambridge, MA: HUP, 1928), public domain (copyright not renewed), adapted by Harland.
2 . . . (3) Be that as it may, Boiotia in earlier times was inhabited by barbarians, the Aonians and the Temmikians, who wandered there from Sounion, and by the Lelegians and the Hyantians. Then the Phoenicians occupied it, I mean the Phoenicians with Kadmos, the man who fortified the Kadmeia and left the dominion to his descendants. Those Phoenicians founded Thebes in addition to the Kadmeia, and preserved their dominion, commanding most of the Boiotians until the expedition of the Epigonians. On this occasion they left Thebes for a short time, but came back again. In the same way, when they were ejected by the Thracians and the Pelasgians, they established their government in Thessaly along with the Arnaians for a long time, so that they were all called Boiotians.
Then they returned to the homeland, at the time when the Aiolian fleet, near Aulis in Boiotia, was now ready to set sail, I mean the fleet which the sons of Orestes were despatching to Asia.