1. Rosenfeld, W. D., J. Amer. Oil Chemists Soc., 44, 703 (1967).
2. Meinsshein, W. G., Bull Amer. Assoc. Petrol. Geol., 43, 925 (1959); Geochim Cosmochim. Acta, 22, 58 (1961).
3. Marcusson, J., Chem. Z., 32, 377, 391 (1908).
4. Louis, M., Rev. Inst. Franc, du Pétrole, 19, 277 (1964); Danieli, N., Gil-Av, E., and Louis, M., Nature (in the press).
5. Burlingame, A. L., Haug, P., Belsky, T., and Calvin, M., Proc. US Nut. Acad. Sci., 54, 1406 (1965).