| title | ISBN-13 | year of publication |
|---|---|---|
| Fireflies in the night | 978-0-06-022484-4 | 1991 |
| Fireflies in the Night | 978-0-06-022485-1 | 1991 |
| Fireflies in the Night: Revised Edition | 978-0-06-445101-7 | 1991 |
| Why Frogs Are Wet | 978-0-06-445195-6 | 2000 |
| Why Frogs Are Wet | 978-0-06-445043-0 | 1987 |