1. Adesanwo OO, Adetunji MT, Dunlevey JN, Diatta S, Osiname OA, Adesanwo JK (2009) X-ray fluorescence studies of Ogun phosphate rocks. Electron J Environ Agric Food Chem 8(10):1052–1061
2. Al-Bassam K, Al-Dahan A, Jamil A (1983) Campanian–Maastrichtian phosphorites of Iraq. Petrology, geochemistry and genesis. Mineral Depos 18:215–233
3. Altschuler ZS (1980) The geochemistry of trace elements in marine phosphorites: part 1. Characteristic abundances and enrichment, marine phosphorites. SEPM Spec Publi 29:19–30
4. Altschuler ZS, Clarke RS, Young EY (1958) Geochemistry of uranium in apatite and phosphorite. US Geol Surv Prof Pap 314-D:45–90
5. Arning ET, Lückge A, Breuer C, Gussone N, Birgel D, Peckmann J (2009) Genesis of phosphorite crusts off Peru. Mar Geol 262:68–81