1. American Society for Testing Materials, Manual on Measurement and Sampling of Petroleum and Petroleum Products 1957, Methods D270–57 T, D923–56, D1145–53.
2. Institute of Petroleum (London), Standard Methods for Testing Petroleum and Its Products Method IP 60/61.
3. American Petroleum Institute, API Standard 2500, Measuring, Sampling and Testing Crude Oil.
4. Essentials of Quantitative Analysis;BENEDETTI-PICHLER,1956
5. Colorimetric Determination of Traces of Metals;SANDELL,1959