Addasiad Cymraeg gan = Welsh adaptation by: Emily Huws.
Argraffiad Saesneg gwreiddiol = Original English edition : Oxford : Oxford University Press, 1996.
Cyfrinach y gôli by Paul Shipton. ISBN 0861745108. Published by Gwasg Addysgol Drake in 2002. Publication and catalogue information, links to buy online and reader comments.