Argraffiad Saesneg gwreiddiol = Original English edition : London : Usborne Publishing, 1989.
Addasiad Cymraeg gan = Welsh adaptation by : Sioned Lleinau.
Yr Ymwelwyr by Heather Amery. ISBN 9781843236726. Published by Gomer in 2005. Publication and catalogue information, links to buy online and reader comments.