(1981). The 1981 world book year book.: The annual supplement to the world book encyclopedia (ed.). World book- childcraft international, Inc..
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रThe 1981 World Book Year Book.: The Annual Supplement to the World Book Encyclopedia. ed. Chicago: World book- childcraft international, Inc., 1981.
एमएलए (9वां संस्करण) प्रशस्ति पत्रThe 1981 World Book Year Book.: The Annual Supplement to the World Book Encyclopedia. ed. World book- childcraft international, Inc., 1981.
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