From Burnet's Note on the Sources
What, then, was the common source of the Placita and the Eclogae? Diels has shown that
Theodoret (c. A.D.445) had access to it; for in some cases he gives a fuller form of statements made in
these two works. Not only so, but he also names that source; for he refers us (Gr. aff. cur. iv. 31)
Ἀετίου τὴν περὶ ἀρεσκόντων συναγωγήν. Diels has accordingly printed the Placita in parallel columns with the relevant parts of the
Eclogae, under the title of Aetii Placita. The quotations from "Plutarch" by later writers, and the
extracts of Theodoret from Aetios, are also given at the foot of each page.