1. Ali, M. F., Bukhari, A., and Saleem, M., 1983, Trace metals in crude oils from Saudi Arabia, Ind. Eng. Chem. Prod. Res. Dev. 22:691–694.
2. Al-Shahristani, H., and Al-Atyia, M. J., 1972, Vertical migration in Iraqi oil fields: Evidence based on vanadium and nickel concentrations, Geochim. Cosmochim. Acta 36:929–938.
3. Baker, E. W., and Louda, J. W., 1984, Highly dealkylated copper and nickel etioporphyrins in marine sediments, Org. Geochem. 6: 183–192.
4. Barton, P. B., 1967, Possible role of organic matter in the precipitation of Mississippi Valley ores, in: Genesis of Stratiform Lead-Zinc-Barite-Fluorite Deposits in Carbonate Rocks (J. S. Brown, ed.), Econ. Geol. Monograph No. 3, pp. 371–378.
5. Barwise, A. J. G., and Whitehead, E. V., 1980, Separation and structure of petroporphyrins, in: Advances in Organic Geochemistry 1979 (A. G. Douglas and J. R. Maxwell, eds.), Physics and Chemistry of the Earth, Pergamon Press, Oxford, Vol. 12, pp. 181–192.