An Official TOEFL Study Aid. (1989). Understanding TOEFL: Workbook. USA: Educational Testing Service.
シカゴスタイル引用形An Official TOEFL Study Aid. Understanding TOEFL: Workbook. USA: Educational Testing Service, 1989.
MLA引用形式An Official TOEFL Study Aid. Understanding TOEFL: Workbook. USA: Educational Testing Service, 1989.
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