Educational Testing Service. (2007). The official guide to the new toefl ibt. McGraw-Hill.
Chicago Style (17th ed.) ZitazioaEducational Testing Service. The Official Guide to the New Toefl Ibt. New York: McGraw-Hill, 2007.
MLA (9th ed.) ZitazioaEducational Testing Service. The Official Guide to the New Toefl Ibt. McGraw-Hill, 2007.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.