1. J.G. Speight, The chemistry and technology of petroleum, 2nd Ed., Marcel Dekker, USA (1991).
2. M.R. Gray, Y. Zhao, C.M. McKnight, D.A. Komar and J. D. Carruthers, Energy Fuels, 13(5), 1037 (1999).
3. J. D. Miller and M. Misra, Fuel Process. Technol., 6(1), 27 (1982).
4. R. M. Butler, US Patent, 4,344,485 (1982).
5. T. P. Clarke, US Patent, 4,240,897 (1980).