Warshawsky, D. (1994). Spectrum 4: A communicative course in English. Workbook. Prentice Hall Regents.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रWarshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. London: Prentice Hall Regents, 1994.
एमएलए (9वां संस्करण) प्रशस्ति पत्रWarshawsky, Diane. Spectrum 4: A Communicative Course in English. Workbook. Prentice Hall Regents, 1994.
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