Não informado. (1971). Environmental data service. Environmental Data Service.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Environmental Data Service. Rockville, Md: Environmental Data Service, 1971.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Environmental Data Service. Environmental Data Service, 1971.
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