Não informado. (1988). 21st. Century science & technology. 21st. Century Science Associates.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. 21st. Century Science & Technology. Washington: 21st. Century Science Associates, 1988.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. 21st. Century Science & Technology. 21st. Century Science Associates, 1988.
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