Lucius Cassius Dio Cocceianus (229): «Book LIV, Ch 32», i: Cary, Earnest (oversetter), Dio's Roman History, VI, London: William Heinemann, 1917, s. 365
rug.nl
dissertations.ub.rug.nl
Looijenga, Jantina Helena (1997): «History, Archaeology and Runes»Arkivert 2. mai 2005 hos Wayback Machine. (PDF) i: SSG Uitgeverij, Runes Around the North Sea and on the Continent AD 150–700; Texts and Contexts (PhD doktoravhandling), Groningen: Groningen University, s. 30, ISBN 90-6781-014-2. Looijenga siterer Gerrets' The Anglo-Frisian Relationship Seen from an Archaeological Point of View (1995) for denne påstanden.
web.archive.org
Looijenga, Jantina Helena (1997): «History, Archaeology and Runes»Arkivert 2. mai 2005 hos Wayback Machine. (PDF) i: SSG Uitgeverij, Runes Around the North Sea and on the Continent AD 150–700; Texts and Contexts (PhD doktoravhandling), Groningen: Groningen University, s. 30, ISBN 90-6781-014-2. Looijenga siterer Gerrets' The Anglo-Frisian Relationship Seen from an Archaeological Point of View (1995) for denne påstanden.
