Arg. Saesneg gwreiddiol = Original English ed.: Harlow: Addison Wesley Longman Limited, 1996.
Teitl clawr = Cover title.
Testun ar y cloriau mewnol = Text on inside covers.
Grymoedd yn gweithredu by George Snape. ISBN 1860853900. Published by Uned Iaith Genedlaethol Cymru CBAC in 1998. Publication and catalogue information, links to buy online and reader comments.