Jelaskan Sumber dari Erwigius

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Murphy, Francis X. "Julian of Toledo and the Fall of the Visigothic Kingdom in Spain." Speculum, Vol. 27, No. 1. (January, 1952), pp 1–27.

Thompson, E. A.. The Goths in Spain. Oxford: Clarendon Press, 1969.

Continuité des élites à Byzance durante les siècles obscurs. Les princes caucasiens et l'Empire du VIe au IXe siècle. 2006.