Agricultural Resources & Environmental Indicators. United States Department of Agriculture.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रAgricultural Resources & Environmental Indicators. United States Department of Agriculture.
एमएलए (9वां संस्करण) प्रशस्ति पत्रAgricultural Resources & Environmental Indicators. United States Department of Agriculture.
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