Kouraim, M.N., Fawzy, M.M. and Helaly, O.S. 2014. Leaching of Lanthanides from Phosphogypsum Waste using Nonyl Phenol Ethoxylate Associated with HNO3 and HCl. International Journal of Sciences: Basic and Applied Research (IJSBAR). 16, 2 (Jun. 2014), 31–44.