1. Generalisation of Geological Data on Hard Minerals;El-Ramly;Geol. Surv. Egypt, Part I, Section A,1970
2. Wet- Process High Strength Phosphoric Acid Production From Egyptian phosphate Concentrates;Hassan,1993
3. Phosphates and Phosphoric Acid;Becker,1990
4. Use of Acids Other Than Sulphuric Acid :1. Hydrochloric Acid;Baniel,1968