- FRANTZEN A.J., The Literature of Penance in Anglo-Saxon England, New Brunswick 1983, 19.
- MCNEILL J.T., The Celtic Penitentials and their Influence on continental Christianity, Paris 1923, 31.
- MEENS R., Penance in Medieval Europe 600–1200, Cambridge 2014, 40-43.
- OAKLEY T.P., English Penitential Discipline and Anglo-Saxon Law, New York 1923, 36-37.