Arnold, J.C. "Arcadia Becomes Jerusalem: Angelic Caverns and Shrine Conversion at Monte Gargano." Speculum vol. 75 (July 2000), pp. 567–88
N. Everett, "The Liber de apparitione S. Michaelis in Monte Gargano and the hagiography of dispossession", Analecta Bollandiana 120 (2002), 364-391. (Argues that the Liber reflects conflict between the churches of Siponto and Benevento over control of the Gargano shrine, and that the Liber dates c.663-750).
