- Delta's Key to the Next Generation TOEFL Test: Advanced Skill Practice Book
- Delta's Key to the TOEFL Test
- Delta's Key to the TOEFL iBT: Advanced Skill Practice [With CD (Audio)]
- Delta's Key to the Next Generation TOEFL® Test: Essential Grammar for the iBT
- Delta's Key to the TOEFL Ibt: Seven Practice Tests - Revised Edition W/ MP3 Audio CD