Khalil, A. A. R. (1990). Genesis and ecology of the vertisols of Eastern Sudan. Christian-Albrechts-Universitat zu Kiel.
Lua i Stíl Chicago (17ú heag.)Khalil, Ahmed Abdel Raouf. Genesis and Ecology of the Vertisols of Eastern Sudan. Kiel: Christian-Albrechts-Universitat zu Kiel, 1990.
Lua MLA (8ú heag.)Khalil, Ahmed Abdel Raouf. Genesis and Ecology of the Vertisols of Eastern Sudan. Christian-Albrechts-Universitat zu Kiel, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.