Ralph, P. L. (1997). World civilizations, their history and their culture (9th ed.). W.W. Norton.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रRalph, Philip Lee. World Civilizations, Their History and Their Culture. 9th ed. New York: W.W. Norton, 1997.
एमएलए (8वां संस्करण) प्रशस्ति पत्रRalph, Philip Lee. World Civilizations, Their History and Their Culture. 9th ed. W.W. Norton, 1997.
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