Helzer. The Ecology and Management of Prairies in the Central United States. University of Iowa Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रHelzer. The Ecology and Management of Prairies in the Central United States. University of Iowa Press.
एमएलए (9वां संस्करण) प्रशस्ति पत्रHelzer. The Ecology and Management of Prairies in the Central United States. University of Iowa Press.
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