The International English School. (2007). TOEFL next generation IBT internet based TOEFL: Student Book.
Trích dẫn kiểu ChicagoThe International English School. TOEFL Next Generation IBT Internet Based TOEFL: Student Book. 2007.
Trích dẫn MLAThe International English School. TOEFL Next Generation IBT Internet Based TOEFL: Student Book. 2007.
Cảnh báo: Các trích dẫn này có thể không phải lúc nào cũng chính xác 100%.