1. A Voorhees and U. U. Smith, in: Newest Advances in Petroleum Chemistry and Petroleum Refining [Russian translation], Vols. 7?8, Khimiya, Moscow (1968), p. 250.
2. A. N. Plyusnin, and V. V. Leonenko, Neftekhimiya, 16, 672 (1976).
3. Ya. B. Chetkov, Nonhydrocarbon Compounds in Petroleum Products [in Russian], Khimiya, Moscow (1964), p. 81.
4. S. L. Gusinskaya, Petroleum Oils of Southern Uzbekistan [in Russian], Tashkent (1965), p. 100.
5. G. Costantinides and G. Arich, in: Fundamental Aspects of Petroleum Geochemistry, Elsevier, New York (1967), Chap. 4, p. 155.