1. Institute of Petroleum, Method for Analysis and Testing, IP 69/78, part 1, Vol. 1, Heyden and Son, London.
2. Ibid Institute of Petroleum, Method for Analysis and Testing, IP 344/80, part 1, vol. 2.
3. Unpublished work.
4. W. J. Podbielniak, Ind. Eng. Chem. Anal. Ed.,3, 177 (1931).
5. W. K. Al-Thamir, J. H. Purnell, R. J. Laub, J. Chromatogr.,188, 79 (1980).