C.D. · C. Duffy · Carolyn B. Duffy
| title | ISBN-13 (ISBN-10) | year of publica- tion | other author(s) |
|---|---|---|---|
| Delta Heinemann Toefl: Preparation Coursebook | 978-0-435-26309-6 (0-435-26309-9) | 1993 | |
| The Heinemann Toefl Preparation Course | 978-0-435-26310-2 (0-435-26310-2) | 1992 | |
| Toefl Practice Tests | 978-0-435-26321-8 (0-435-26321-8) | 1996 | M.Kathleen Mahnke |