Warshawsky, D. (1994). Spectrum 4: A communicative course in English. Workbook. Prentice Hall Regents.
Citazione stile Chigago Style (17a edizione)Warshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. London: Prentice Hall Regents, 1994.
Citatione MLA (9a ed.)Warshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. Prentice Hall Regents, 1994.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.