1. Siemens R.E., Jong B.W. and Russel J.H..(1986) “Potential of Spent Catalysts as a Source of Critical Metals”, Conservation and Recycling, 9(2), pp 189–196
2. Biswas R.K., Wakihara M. and Taniguchi M.,(1986) “Characterisation and Leaching of the Heavy Oil Desulphurisation Waste Catalyst”, Bangladesh J.Sci.Ind.Res., 21, pp 228–237
3. Sefton V.B., Fox R. and Lorenz W.P., (1989) “Recovery and Separation of Metals from Spent Petroleum Refining Catalyst.” US Patent 4, 861, 565., 29 Aug
4. Mukherjee T., Chakraborty S., Bidaye A. and Gupta C.,(1990) “Recovery of Pure Vanadium Oxide from Bayer Sludge.” Minerals Engineering 3(3/4), pp 345–353
5. Cotton F.A.and Wilkinson G., (1972) “Advanced Inorganic Chemistry. A Comprehensive Text.” 3rd.Edition, Interscience New York