Cyhoeddwyd dan nawdd = Published under auspices of: Uned Iaith Genedlaethol Cymru, CBAC.
OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
Stiwdio 8 by Huw Lloyd. ISBN 185902078X. Published by Gomer in 1993. Publication and catalogue information, links to buy online and reader comments.