Gwasg Cambria · Solution Tree Press
| title | ISBN-13 (ISBN-10) | year of publication |
|---|---|---|
| Gweld y byd, a storïau eraill | 978-0-900439-02-5 (0-900439-02-5) | 1971 |
| Unlocked: Assessment as the Key to Everyday Creativity in the Classroom | 978-1-947604-51-3 (1-947604-51-1) | 2019 |