Warshawsky, D. (1994). Spectrum 4: A communicative course in English. Workbook. Prentice Hall Regents.
Lua i Stíl Chicago (17ú heag.)Warshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. London: Prentice Hall Regents, 1994.
Lua MLA (9ú heag.)Warshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. Prentice Hall Regents, 1994.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.