Thegan, The Deeds of Emperor Louis, in Charlemagne and Louis the Pious: The Lives by Einhard, Notker, Ermoldus, Thegan, and the Astronomer, trans. Thomas F. X. Noble (University Park: Pennsylvania State University Press, 2009), 209; Agobard of Lyons, Liber apologeticus I, in Opera Omnia, ed. L. van Acker, Corpus Christianorum Continuatio Mediaevalis, vol. 52 (Turnhout, Belgium: Brepols, 1981), 309–310.
