Angelsaksische kroniek s.a. 495, Jan van Worcester, Chronicon ex chronicis I (p. 272 = West-Saksische koningslijst). B. Yorke, art. Ceolwulf (d. 611?), in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie – betalend)
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books.google.be
B. Yorke, Kings and Kingdoms of early Anglo-Saxon England, Londen - New York, 2002, p. 133. Gearchiveerd op 10 juni 2023.
oxforddnb.com
B. Yorke, art. Cwichelm, in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie[dode link] – betalend)
web.archive.org
B. Yorke, Kings and Kingdoms of early Anglo-Saxon England, Londen - New York, 2002, p. 133. Gearchiveerd op 10 juni 2023.
B. Yorke, art. Ceol, in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie – betalend)
Angelsaksische kroniek s.a. 495, Jan van Worcester, Chronicon ex chronicis I (p. 272 = West-Saksische koningslijst). B. Yorke, art. Ceolwulf (d. 611?), in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie – betalend)
B. Yorke, art. Ceolwulf (d. 611?), in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie – betalend)
Angelsaksische kroniek s.a. 611. Vgl. B. Yorke, art. Ceolwulf (d. 611?), in Oxford Dictionary of National Biography, Oxford, 2004. (digitale versie – betalend)