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 Juli 25, 2024. http://bsb0sit-zepweb01.bsb.lrz.de/portal/index.php/sof/article/view/7597.