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2. Cex, B. B., Bull. Amer. Assoc. Petrol. Geol., 30, 645 (1946).
3. Smith, P. V., Bull. Amer. Assoc. Petrol. Geol., 38, 377 (1954). Stevens, N. P., Bray, E. E., and Evans, E. D., Bull. Amer. Assoc. Petrol. Geol., 40, 975 (1956).
4. Marcusson, J., Chem. Ztg., 32, 377, 391 (1908). Whitmore, F. C., A.P.I. Besearch Project 43 B, Proc. Amer. Petrol. Inst., 25, 100 (1945).
5. Treibs, A., Annalen, 519, 42 (1934).