Khalil, A. A. R. (1990). Genesis and ecology of the vertisols of Eastern Sudan. Christian-Albrechts-Universitat zu Kiel.
Čikaški stil citiranja (17. izdanje)Khalil, Ahmed Abdel Raouf. Genesis and Ecology of the Vertisols of Eastern Sudan. Kiel: Christian-Albrechts-Universitat zu Kiel, 1990.
MLA način citiranja (8. izdanje)Khalil, Ahmed Abdel Raouf. Genesis and Ecology of the Vertisols of Eastern Sudan. Christian-Albrechts-Universitat zu Kiel, 1990.
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