1. M. Mew, First green shoots of recovery. (Phosphate rock industry), 12th Annual Survey & Outlook (Industry Overview) Engineering & Mining Journal, 1994.
2. P. Colleneneitte, D. J. Graigner, Mineral resources of Saudi-Arabia, Ministry of Petroleum and Mineral Resources, Directorate General of Mineral Resources, Special Publication 2, Jeddah, Saudi-Arabia, 1994, p. 322.
3. F. Z. Khiari, A. Aksoy, A. Sahin, J. Radioanal. Nucl. Chem., 261 (2004) 507.
4. N. Dylevskaia, Phosagro, IFA Technical Conference, Chennai, India, September, 2002.
5. J. B. Cowart, W. C. Burnett, J Environ Qual., 23 (1994) 651.