HOPKINS, J. A. Farm Records And Accounting John A. Hopkins And Earl O. Heady. Iowa State University Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रHOPKINS, John A. Farm Records And Accounting John A. Hopkins And Earl O. Heady. Iowa State University Press.
एमएलए (8वां संस्करण) प्रशस्ति पत्रHOPKINS, John A. Farm Records And Accounting John A. Hopkins And Earl O. Heady. Iowa State University Press.
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