History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
And they advised him to attack the Apodotians first, then the Ophioneans, and after them the Eurytanians. These last constitute the largest division of the Aetolians, their speech is more unintelligible than that of the other Aetolians, and, according to report, they are eaters of raw flesh. If these tribes were subdued, they said, the rest would readily yield.
Demosthenes was induced to make this decision, not only by his desire to please the Messenians, but chiefly because he thought that, without help from Athens, he would be able with his allies from the mainland, once the Aetolians had joined him, to make an overland expedition against the Boeotians by passing through the country of the Ozolian Locrians to Cytinium in Doris, keeping Parnassus on the right, until he should descend into Phocian territory. The Phocians would presumably be eager to join the expedition in view of their traditional friendship with Athens, or else could be forced to do so; and Phocis is on the very borders of Boeotia. So he set sail from Leucas with his whole armament in spite of the unwillingness of the Acarnanians and went along the coast to Sollium.