Brynley F. Roberts. "Geoffrey of Monmouth, Historia Regum Britanniae and Brut y Brenhinedd". e-barzh The Arthur of the Welsh: The Arthurian Legend in Medieval Welsh Literature gant R. Bromwich, A. O. H. Jarman ha Brynley F. Roberts, pp. 97–116. (Gwasg Prifysgol Cymru, 1991).