Christopherson, R. W. (2009). Geosystems: An introduction to physical geography (7th ed., custom ed.). Pearson Custom Pub.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रChristopherson, Robert W. Geosystems: An Introduction to Physical Geography. 7th ed., custom ed. New York: Pearson Custom Pub, 2009.
एमएलए (9वां संस्करण) प्रशस्ति पत्रChristopherson, Robert W. Geosystems: An Introduction to Physical Geography. 7th ed., custom ed. Pearson Custom Pub, 2009.
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