TOEFL practice tests: Test of English as a Foreign Language. ETS Educational Testing Service.
Chicago-Zitierstil (17. Ausg.)TOEFL Practice Tests: Test of English as a Foreign Language. Princeton, N.J: ETS Educational Testing Service.
MLA-Zitierstil (9. Ausg.)TOEFL Practice Tests: Test of English as a Foreign Language. ETS Educational Testing Service.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.