Bartrum Peter C. Y Pedwar Brenin ar hugain a farnwyd yn gadarnaf (The Twenty Four Kings Judged to be the Mightiest) . In: Etudes Celtiques, vol. 12, fascicule 1, 1968. pp. 157-194.
Bartrum Peter C. Tri Thlws ar Ddeg Ynys Brydain (The Thirteen Treasures of the Island of Britain). In: Etudes Celtiques, vol. 10, fascicule 2, 1963. pp. 434-477.
