1. J. G. Speight, The Chemistry and Technology of Petroleum, 4th ed., Taylor & Francis Group, 2006.
2. J. G. Speight, Handbook of Petroleum Product Analysis, New Jersey: John Wiley & Sons, 2002.
3. I. M. Dittert, J. S. A. Silva, R. G. O. Araujo, A. J. Curtius, B. Welz, and H. Becker-Ross, Spectrochim. Acta Pt. B, 64, 537 (2009).
4. ASTM D5863–00a: Standard Test Methods for Determination of Nickel, Vanadium, Iron, and Sodium in Crude Oils and Residual Fuels by Flame Atomic Absorption Spectrometry (Reapproved 2005), 2000.
5. ASTM D5708–05: Standard Test Methods for Determination of Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry, 2005.