Jayarava Michael Attwood, Did King Ajātasattu Confess to the Buddha, and Did the Buddha Forgive Him? Journal of Buddhist Ethics (2008), pp. 279-307. Online PDF.
Michael Hahn, Ajātaśatrvavadāna: A Gopadatta Story from Tibet. K. P. Jayaswal Commemoration Volume (Patna 1981), pp. 242-276.
EoB under "Ajātasattu" and under "A-shê-shih-wang-shou-cheüh-ching."
Obeyesekere, Conscience, p. 240 ff. Ajātasattu. Story as told in a 13th century Sinhala text, the Pūjāvaliya.