1. Abdel-Rahman, M. (1980). Geology of the area southeast of Qena with special reference to the phosphate deposits. M.Sc. thesis, Geology Department, Assiut University, Egypt, p. 177.
2. Abdel-Rahman, M. (1992). Geochemical, mineralogical and sedimentological studies on phosphorites of the Nile Valley (Duwi Formation) between Qena and Idfu, Egypt. Ph.D. thesis. Technischen University, Berlin, Germany, p. 163.
3. The geochemistry of uranium and thorium;Adams;Physics and Chemistry of the Earth,1959
4. The lognormal distribution of the elements;Ahrens;Geochimica et Cosmochimica Acta,1954
5. The geochemistry of trace elements in marine phosphorites, Part I;Altschuler;SEPM Special Publication,1980