Bowlus, Charles R. „Archbishop Theotmar of Salzburg’s Letter to Pope John IX. A Forgery of Bishop Pilgrim of Passau?“. Südost-Forschungen 1, no. 1 (November 30, 2021): 1–11. Zugegriffen Mai 2, 2025. https://www.suedost-forschungen.de/portal/index.php/sof/article/view/7597.