H. W. Parke, The Oracles of Zeus: Dodona, Olympia, Ammon (Oxford: Basil Blackwell, 1967).
Hillman cites Parke’s authoritative study of the oracles of Zeus — including Ammon — as a scholarly foundation for the Greek conception of fate and the soul’s calling, linking the Ammonian oracle directly to the daimonic tradition undergirding his acorn theory.
, The Soul’s Code: In Search of Character and Calling, 1996thesis