The earliest English kings

Royal Commission on the Ancient and Historical Monuments of Wales, Royal Commission on Ancient and Historical Monuments in Wales, Jones, Ieuan Gwynedd, Davies, J. L., Davies, J. L. (Jeffrey L), Kirby, D. P., Cardiganshire Antiquarian Society, Kirby, D. P. (David Peter), 1936-, 1994

Royal Commission on Ancient and Historical Monuments in Wales, Jones, Ieuan Gwynedd, Davies, J. L., Kirby, D. P., Cardiganshire Antiquarian Society, 1994

Davies, Wendy, Smith, J. Beverley, Loyn, H. R. (Henry Royston), Kirby, D. P., Carr, A. D. (Anthony D.), 1938-, Dumville, David N., Lambert, Pierre-Yves, 1990

Smyth, Alfred P., Kirby, D. P., Williams, Ann, 1937-, 1991