Gregory, K. J., & Walling, D. E. (1981). Man and environmental processes: A physical geography perspective. Butterworths.
Lua i Stíl Chicago (17ú heag.)Gregory, K. J., agus D. E. Walling. Man and Environmental Processes: A Physical Geography Perspective. London: Butterworths, 1981.
Lua MLA (9ú heag.)Gregory, K. J., agus D. E. Walling. Man and Environmental Processes: A Physical Geography Perspective. Butterworths, 1981.
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