1. Cardon, P.B., 1962. Process for recovering niobium and tantalum from ores and ores concentrates containing same. U.S. Patent 3,058,825.
2. Hydrometallurgical processing of Ta/Nb compounds;Eckert,1995
3. Extraction of niobium and tantalum from nitrate and sulfate media by using MIBK;El-Hussaini;Mineral Processing and Extractive Metallurgy Review,2001
4. Sulfuric acid leaching of Kab Amiri niobium–tantalum bearing minerals, Central Eastern Desert, Egypt;El-Hussaini;Hydrometallurgy,2002
5. Extractive Metallurgy of Niobium;Gupta,1994